diff -uNr mediawiki-1.5.8/includes/Setup.php mw-scripts-158/includes/Setup.php
--- includes/Setup.php	2006-02-11 02:26:47.000000000 -0500
+++ includes/Setup.php	2006-04-14 18:28:29.000000000 -0400
@@ -118,11 +118,11 @@
 wfProfileIn( $fname.'-SetupSession' );
 
 if ( $wgDBprefix ) {
-	$wgCookiePrefix = $wgDBname . '_' . $wgDBprefix;
+	$wgCookiePrefix = str_replace("+", "", $wgDBname . '_' . $wgDBprefix);
 } elseif ( $wgSharedDB ) {
 	$wgCookiePrefix = $wgSharedDB;
 } else {
-	$wgCookiePrefix = $wgDBname;
+	$wgCookiePrefix = str_replace("+", "", $wgDBname);
 }
 
 session_name( $wgCookiePrefix . '_session' );