Index: wp-includes/post-template.php
===================================================================
--- wp-includes/post-template.php	(revision 22928)
+++ wp-includes/post-template.php	(working copy)
@@ -574,7 +574,9 @@
 	if ( empty( $post->post_password ) )
 		return false;
 
-	if ( ! isset( $_COOKIE['wp-postpass_' . COOKIEHASH] ) )
+	$name = "wp-postpass_{$post->ID}" . COOKIEHASH;
+
+	if ( ! isset( $_COOKIE[ $name ] ) || $_COOKIE[ $name ] != $post->post_password )
 		return true;
 
 	if ( empty( $wp_hasher ) ) {
@@ -583,7 +585,7 @@
 		$wp_hasher = new PasswordHash(8, true);
 	}
 
-	$hash = stripslashes( $_COOKIE[ 'wp-postpass_' . COOKIEHASH ] );
+	$hash = stripslashes( $_COOKIE[ $name ] );
 
 	return ! $wp_hasher->CheckPassword( $post->post_password, $hash );
 }
@@ -1221,10 +1223,12 @@
  */
 function get_the_password_form() {
 	$post = get_post();
-	$label = 'pwbox-' . ( empty($post->ID) ? rand() : $post->ID );
+	$id = empty( $post->ID ) ? rand() : $post->ID;
+	$label = 'pwbox-' . $id;
 	$output = '<form action="' . esc_url( site_url( 'wp-login.php?action=postpass', 'login_post' ) ) . '" method="post">
 	<p>' . __("This post is password protected. To view it please enter your password below:") . '</p>
 	<p><label for="' . $label . '">' . __("Password:") . ' <input name="post_password" id="' . $label . '" type="password" size="20" /></label> <input type="submit" name="Submit" value="' . esc_attr__("Submit") . '" /></p>
+	<input type="hidden" name="id" value="' . $id . '" />
 </form>
 	';
 	return apply_filters('the_password_form', $output);
Index: wp-login.php
===================================================================
--- wp-login.php	(revision 22928)
+++ wp-login.php	(working copy)
@@ -396,7 +396,7 @@
 	}
 
 	// 10 days
-	setcookie( 'wp-postpass_' . COOKIEHASH, $wp_hasher->HashPassword( stripslashes( $_POST['post_password'] ) ), time() + 10 * DAY_IN_SECONDS, COOKIEPATH );
+	setcookie( 'wp-postpass_' . $_POST['id'] . COOKIEHASH, $wp_hasher->HashPassword( stripslashes( $_POST['post_password'] ) ), time() + 10 * DAY_IN_SECONDS, COOKIEPATH );
 
 	wp_safe_redirect( wp_get_referer() );
 	exit();