Index: src/wp-includes/js/utils.js
===================================================================
--- src/wp-includes/js/utils.js	(revision 29354)
+++ src/wp-includes/js/utils.js	(working copy)
@@ -3,25 +3,26 @@
 // utility functions
 
 var wpCookies = {
-// The following functions are from Cookie.js class in TinyMCE, Moxiecode, used under LGPL.
+// The following functions are from Cookie.js class in TinyMCE 3, Moxiecode, used under LGPL.
 
-	each : function(obj, cb, scope) {
+	each: function( obj, cb, scope ) {
 		var n, l;
 
-		if ( !obj )
+		if ( ! obj )
 			return 0;
 
 		scope = scope || obj;
 
-		if ( typeof(obj.length) != 'undefined' ) {
+		if ( typeof( obj.length ) !== 'undefined' ) {
 			for ( n = 0, l = obj.length; n < l; n++ ) {
-				if ( cb.call(scope, obj[n], n, obj) === false )
+				if ( cb.call( scope, obj[n], n, obj ) === false ) {
 					return 0;
+				}
 			}
 		} else {
 			for ( n in obj ) {
 				if ( obj.hasOwnProperty(n) ) {
-					if ( cb.call(scope, obj[n], n, obj) === false ) {
+					if ( cb.call( scope, obj[n], n, obj ) === false ) {
 						return 0;
 					}
 				}
@@ -34,17 +35,18 @@
 	 * Get a multi-values cookie.
 	 * Returns a JS object with the name: 'value' pairs.
 	 */
-	getHash : function(name) {
-		var all = this.get(name), ret;
+	getHash: function( name ) {
+		var cookie = this.get( name ), values;
 
-		if ( all ) {
-			this.each( all.split('&'), function(pair) {
+		if ( cookie ) {
+			this.each( cookie.split('&'), function( pair ) {
 				pair = pair.split('=');
-				ret = ret || {};
-				ret[pair[0]] = pair[1];
+				values = values || {};
+				values[pair[0]] = pair[1];
 			});
 		}
-		return ret;
+
+		return values;
 	},
 
 	/**
@@ -52,20 +54,20 @@
 	 *
 	 * 'values_obj' is the JS object that is stored. It is encoded as URI in wpCookies.set().
 	 */
-	setHash : function(name, values_obj, expires, path, domain, secure) {
+	setHash: function( name, values_obj, expires, path, domain, secure ) {
 		var str = '';
 
-		this.each(values_obj, function(val, key) {
-			str += (!str ? '' : '&') + key + '=' + val;
+		this.each( values_obj, function( val, key ) {
+			str += ( ! str ? '' : '&' ) + key + '=' + val;
 		});
 
-		this.set(name, str, expires, path, domain, secure);
+		this.set( name, str, expires, path, domain, secure );
 	},
 
 	/**
 	 * Get a cookie.
 	 */
-	get : function(name) {
+	get: function( name ) {
 		var e, b,
 			cookie = document.cookie,
 			p = name + '=';
@@ -90,7 +92,7 @@
 		if ( e == -1 )
 			e = cookie.length;
 
-		return decodeURIComponent( cookie.substring(b + p.length, e) );
+		return decodeURIComponent( cookie.substring( b + p.length, e ) );
 	},
 
 	/**
@@ -99,13 +101,13 @@
 	 * The 'expires' arg can be either a JS Date() object set to the expiration date (back-compat)
 	 * or the number of seconds until expiration
 	 */
-	set : function(name, value, expires, path, domain, secure) {
+	set: function( name, value, expires, path, domain, secure ) {
 		var d = new Date();
 
-		if ( typeof(expires) == 'object' && expires.toGMTString ) {
+		if ( typeof( expires ) == 'object' && expires.toGMTString ) {
 			expires = expires.toGMTString();
-		} else if ( parseInt(expires, 10) ) {
-			d.setTime( d.getTime() + ( parseInt(expires, 10) * 1000 ) ); // time must be in miliseconds
+		} else if ( parseInt( expires, 10 ) ) {
+			d.setTime( d.getTime() + ( parseInt( expires, 10 ) * 1000 ) ); // time must be in miliseconds
 			expires = d.toGMTString();
 		} else {
 			expires = '';
@@ -123,20 +125,22 @@
 	 *
 	 * This is done by setting it to an empty value and setting the expiration time in the past.
 	 */
-	remove : function(name, path) {
-		this.set(name, '', -1000, path);
+	remove: function( name, path ) {
+		this.set( name, '', -1000, path );
 	}
 };
 
 // Returns the value as string. Second arg or empty string is returned when value is not set.
 function getUserSetting( name, def ) {
-	var obj = getAllUserSettings();
+	var settings = getAllUserSettings();
 
-	if ( obj.hasOwnProperty(name) )
-		return obj[name];
+	if ( settings.hasOwnProperty( name ) ) {
+		return settings[name];
+	}
 
-	if ( typeof def != 'undefined' )
+	if ( typeof def !== 'undefined' ) {
 		return def;
+	}
 
 	return '';
 }
@@ -147,17 +151,36 @@
 	if ( 'object' !== typeof userSettings )
 		return false;
 
-	var cookie = 'wp-settings-' + userSettings.uid, all = wpCookies.getHash(cookie) || {}, path = userSettings.url,
-	n = name.toString().replace(/[^A-Za-z0-9_]/, ''), v = value.toString().replace(/[^A-Za-z0-9_]/, '');
+	var uid = userSettings.uid,
+		oldUid = uid.lastIndexOf('-') > 0 ? uid.substring( 0, uid.lastIndexOf('-') ) : 0,
+		settings = wpCookies.getHash( 'wp-settings-' + uid ),
+		path = userSettings.url;
 
+	name = name.toString().replace( /[^A-Za-z0-9_]/, '' );
+	value = value.toString().replace( /[^A-Za-z0-9_]/, '' );
+
+	// This should be removed in about a year as these cookies will expire by then.
+	if ( oldUid ) {
+		if ( ! settings ) {
+			settings = wpCookies.getHash( 'wp-settings-' + oldUid );
+		}
+		// Delete old cookies
+		if ( wpCookies.get( 'wp-settings-time-' + oldUid ) ) {
+			wpCookies.remove( 'wp-settings-' + oldUid, path );
+			wpCookies.remove( 'wp-settings-time-' + oldUid, path );
+		}
+	}
+
+	settings = settings || {};
+
 	if ( _del ) {
-		delete all[n];
+		delete settings[name];
 	} else {
-		all[n] = v;
+		settings[name] = value;
 	}
 
-	wpCookies.setHash(cookie, all, 31536000, path);
-	wpCookies.set('wp-settings-time-'+userSettings.uid, userSettings.time, 31536000, path);
+	wpCookies.setHash( 'wp-settings-' + uid, settings, 31536000, path );
+	wpCookies.set( 'wp-settings-time-' + uid, userSettings.time, 31536000, path );
 
 	return name;
 }
@@ -168,8 +191,18 @@
 
 // Returns all settings as js object.
 function getAllUserSettings() {
-	if ( 'object' !== typeof userSettings )
+	if ( 'object' !== typeof userSettings ) {
 		return {};
+	}
 
-	return wpCookies.getHash('wp-settings-' + userSettings.uid) || {};
+	var uid = userSettings.uid,
+		settings = wpCookies.getHash( 'wp-settings-' + uid );
+
+	// Try the old format cookie
+	if ( ! settings && uid.lastIndexOf('-') > 0 ) {
+		uid = uid.substring( 0, uid.lastIndexOf('-') );
+		settings = wpCookies.getHash( 'wp-settings-' + uid );
+	}
+
+	return settings || {};
 }
Index: src/wp-includes/option.php
===================================================================
--- src/wp-includes/option.php	(revision 29354)
+++ src/wp-includes/option.php	(working copy)
@@ -713,22 +713,23 @@
  */
 function wp_user_settings() {
 
-	if ( ! is_admin() )
+	if ( ! is_admin() || defined( 'DOING_AJAX' ) ) {
 		return;
+	}
 
-	if ( defined('DOING_AJAX') )
+	if ( ! $user_id = get_current_user_id() ) {
 		return;
+	}
 
-	if ( ! $user_id = get_current_user_id() )
+	if ( is_super_admin() && ! is_user_member_of_blog() ) {
 		return;
+	}
 
-	if ( is_super_admin() && ! is_user_member_of_blog() )
-		return;
-
 	$settings = (string) get_user_option( 'user-settings', $user_id );
+	$uid = $user_id . '-' . get_current_blog_id();
 
-	if ( isset( $_COOKIE['wp-settings-' . $user_id] ) ) {
-		$cookie = preg_replace( '/[^A-Za-z0-9=&_]/', '', $_COOKIE['wp-settings-' . $user_id] );
+	if ( isset( $_COOKIE['wp-settings-' . $uid] ) ) {
+		$cookie = preg_replace( '/[^A-Za-z0-9=&_]/', '', $_COOKIE['wp-settings-' . $uid] );
 
 		// No change or both empty
 		if ( $cookie == $settings )
@@ -735,7 +736,7 @@
 			return;
 
 		$last_saved = (int) get_user_option( 'user-settings-time', $user_id );
-		$current = isset( $_COOKIE['wp-settings-time-' . $user_id]) ? preg_replace( '/[^0-9]/', '', $_COOKIE['wp-settings-time-' . $user_id] ) : 0;
+		$current = isset( $_COOKIE['wp-settings-time-' . $uid]) ? preg_replace( '/[^0-9]/', '', $_COOKIE['wp-settings-time-' . $uid] ) : 0;
 
 		// The cookie is newer than the saved value. Update the user_option and leave the cookie as-is
 		if ( $current > $last_saved ) {
@@ -747,9 +748,9 @@
 
 	// The cookie is not set in the current browser or the saved value is newer.
 	$secure = ( 'https' === parse_url( site_url(), PHP_URL_SCHEME ) );
-	setcookie( 'wp-settings-' . $user_id, $settings, time() + YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN, $secure );
-	setcookie( 'wp-settings-time-' . $user_id, time(), time() + YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN, $secure );
-	$_COOKIE['wp-settings-' . $user_id] = $settings;
+	setcookie( 'wp-settings-' . $uid, $settings, time() + YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN, $secure );
+	setcookie( 'wp-settings-time-' . $uid, time(), time() + YEAR_IN_SECONDS, SITECOOKIEPATH, COOKIE_DOMAIN, $secure );
+	$_COOKIE['wp-settings-' . $uid] = $settings;
 }
 
 /**
@@ -781,8 +782,9 @@
  */
 function set_user_setting( $name, $value ) {
 
-	if ( headers_sent() )
+	if ( headers_sent() ) {
 		return false;
+	}
 
 	$all_user_settings = get_all_user_settings();
 	$all_user_settings[$name] = $value;
@@ -803,8 +805,9 @@
  */
 function delete_user_setting( $names ) {
 
-	if ( headers_sent() )
+	if ( headers_sent() ) {
 		return false;
+	}
 
 	$all_user_settings = get_all_user_settings();
 	$names = (array) $names;
@@ -817,8 +820,9 @@
 		}
 	}
 
-	if ( $deleted )
+	if ( $deleted ) {
 		return wp_set_all_user_settings( $all_user_settings );
+	}
 
 	return false;
 }
@@ -833,22 +837,28 @@
 function get_all_user_settings() {
 	global $_updated_user_settings;
 
-	if ( ! $user_id = get_current_user_id() )
+	if ( ! $user_id = get_current_user_id() ) {
 		return array();
+	}
 
-	if ( isset( $_updated_user_settings ) && is_array( $_updated_user_settings ) )
+	if ( isset( $_updated_user_settings ) && is_array( $_updated_user_settings ) ) {
 		return $_updated_user_settings;
+	}
 
 	$user_settings = array();
-	if ( isset( $_COOKIE['wp-settings-' . $user_id] ) ) {
+	$uid = $user_id . '-' . get_current_blog_id();
+
+	if ( isset( $_COOKIE['wp-settings-' . $uid] ) ) {
+		$cookie = preg_replace( '/[^A-Za-z0-9=&_]/', '', $_COOKIE['wp-settings-' . $uid] );
+	} elseif ( isset( $_COOKIE['wp-settings-' . $user_id] ) ) {
 		$cookie = preg_replace( '/[^A-Za-z0-9=&_]/', '', $_COOKIE['wp-settings-' . $user_id] );
+	}
 
-		if ( $cookie && strpos( $cookie, '=' ) ) // '=' cannot be 1st char
-			parse_str( $cookie, $user_settings );
-
+	if ( ! empty( $cookie ) && strpos( $cookie, '=' ) ) { // '=' cannot be 1st char
+		parse_str( $cookie, $user_settings );
 	} else {
 		$option = get_user_option( 'user-settings', $user_id );
-		if ( $option && is_string($option) )
+		if ( $option && is_string( $option ) )
 			parse_str( $option, $user_settings );
 	}
 
@@ -867,11 +877,13 @@
 function wp_set_all_user_settings( $user_settings ) {
 	global $_updated_user_settings;
 
-	if ( ! $user_id = get_current_user_id() )
+	if ( ! $user_id = get_current_user_id() ) {
 		return false;
+	}
 
-	if ( is_super_admin() && ! is_user_member_of_blog() )
+	if ( is_super_admin() && ! is_user_member_of_blog() ) {
 		return;
+	}
 
 	$settings = '';
 	foreach ( $user_settings as $name => $value ) {
@@ -878,11 +890,12 @@
 		$_name = preg_replace( '/[^A-Za-z0-9_]+/', '', $name );
 		$_value = preg_replace( '/[^A-Za-z0-9_]+/', '', $value );
 
-		if ( ! empty( $_name ) )
+		if ( ! empty( $_name ) ) {
 			$settings .= $_name . '=' . $_value . '&';
+		}
 	}
 
-	$settings = rtrim($settings, '&');
+	$settings = rtrim( $settings, '&' );
 	parse_str( $settings, $_updated_user_settings );
 
 	update_user_option( $user_id, 'user-settings', $settings, false );
@@ -897,11 +910,13 @@
  * @since 2.7.0
  */
 function delete_all_user_settings() {
-	if ( ! $user_id = get_current_user_id() )
+	if ( ! $user_id = get_current_user_id() ) {
 		return;
+	}
 
+	$uid = $user_id . '-' . get_current_blog_id();
 	update_user_option( $user_id, 'user-settings', '', false );
-	setcookie('wp-settings-' . $user_id, ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH);
+	setcookie( 'wp-settings-' . $uid, ' ', time() - YEAR_IN_SECONDS, SITECOOKIEPATH );
 }
 
 /**
Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 29354)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -72,7 +72,7 @@
 	$scripts->add( 'utils', "/wp-includes/js/utils$suffix.js" );
 	did_action( 'init' ) && $scripts->localize( 'utils', 'userSettings', array(
 		'url' => (string) SITECOOKIEPATH,
-		'uid' => (string) get_current_user_id(),
+		'uid' => get_current_user_id() . '-' . get_current_blog_id(),
 		'time' => (string) time(),
 	) );