Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 8577)
+++ wp-includes/formatting.php	(working copy)
@@ -1147,7 +1147,7 @@
 	$original_url = $url;
 
 	if ('' == $url) return $url;
-	$url = preg_replace('|[^a-z0-9-~+_.?#=!&;,/:%@()\\x80-\\xff]|i', '', $url);
+	$url = preg_replace('|[^a-z0-9-~+_.?#=!&;,/:%@$*\'()\\x80-\\xff]|i', '', $url);
 	$strip = array('%0d', '%0a');
 	$url = str_replace($strip, '', $url);
 	$url = str_replace(';//', '://', $url);
@@ -1159,9 +1159,11 @@
 		substr( $url, 0, 1 ) != '/' && !preg_match('/^[a-z0-9-]+?\.php/i', $url) )
 		$url = 'http://' . $url;
 
-	// Replace ampersands ony when displaying.
-	if ( 'display' == $context )
+	// Replace ampersands and single quotes ony when displaying.
+	if ( 'display' == $context ) {
 		$url = preg_replace('/&([^#])(?![a-z]{2,8};)/', '&$1', $url);
+		$url = str_replace( "'", ''', $url );
+	}
 
 	if ( !is_array($protocols) )
 		$protocols = array('http', 'https', 'ftp', 'ftps', 'mailto', 'news', 'irc', 'gopher', 'nntp', 'feed', 'telnet');