diff -urN wordpress-3.0.3.orig//wp-includes/ms-settings.php wordpress-3.0.3/wp-includes/ms-settings.php
--- wordpress-3.0.3.orig//wp-includes/ms-settings.php	2010-05-04 21:48:28.000000000 +0100
+++ wordpress-3.0.3/wp-includes/ms-settings.php	2010-12-22 10:53:13.000000000 +0000
@@ -26,18 +26,8 @@
 
 if ( !isset( $current_site ) || !isset( $current_blog ) ) {
 
+	$_SERVER['HTTP_HOST'] = preg_replace( '|:\d+$|', '', $_SERVER['HTTP_HOST'] );
 	$domain = addslashes( $_SERVER['HTTP_HOST'] );
-	if ( false !== strpos( $domain, ':' ) ) {
-		if ( substr( $domain, -3 ) == ':80' ) {
-			$domain = substr( $domain, 0, -3 );
-			$_SERVER['HTTP_HOST'] = substr( $_SERVER['HTTP_HOST'], 0, -3 );
-		} elseif ( substr( $domain, -4 ) == ':443' ) {
-			$domain = substr( $domain, 0, -4 );
-			$_SERVER['HTTP_HOST'] = substr( $_SERVER['HTTP_HOST'], 0, -4 );
-		} else {
-			wp_die( /*WP_I18N_NO_PORT_NUMBER*/'Multisite only works without the port number in the URL.'/*/WP_I18N_NO_PORT_NUMBER*/ );
-		}
-	}
 
 	$domain = rtrim( $domain, '.' );
 	$cookie_domain = $domain;