Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 17614)
+++ wp-includes/formatting.php	(working copy)
@@ -755,7 +755,7 @@
 	$username = remove_accents( $username );
 	// Kill octets
 	$username = preg_replace( '|%([a-fA-F0-9][a-fA-F0-9])|', '', $username );
-	$username = preg_replace( '/&.+?;/', '', $username ); // Kill entities
+	$username = preg_replace( '/&\w+?;/', '', $username ); // Kill entities
 
 	// If strict, reduce to ASCII for max portability.
 	if ( $strict )
@@ -845,7 +845,7 @@
 	}
 
 	$title = strtolower($title);
-	$title = preg_replace('/&.+?;/', '', $title); // kill entities
+	$title = preg_replace('/&\w.+?;/', '', $title); // kill entities
 	$title = str_replace('.', '-', $title);
 	$title = preg_replace('/[^%a-z0-9 _-]/', '', $title);
 	$title = preg_replace('/\s+/', '-', $title);