Removed the $userpage parameter from Namespace_Default::error_404(). It screwed up a couple plugins. (Thanks Mazza for discovering the issue)
/*
* Auto-completing page/username fields
* NOTE: A more efficient version of the username field is used for Mozilla browsers. The updated code is in autofill.js.
*/
//
// **** 1.1.5: DEPRECATED ****
// Replaced with jQuery-based mechanism.
//