[BirdOPrey5]

Wow... 1.0.0 is a super-simple script... there is really nothing that can go wrong. A lot of people seem to be using it without this issue. Is it possible there is something on your site that somehow overrides the data sent when a 404 or similar error message is generated?

I really can't conceive how this mod could be causing the error because, especially version 1.0.0, you can see the only plugins are on error_ hooks which mean the code isn't even ran until vBulletin is already set to produce an error. If vBulletin is in error mode for example then the css isn't going to be returned anyway on a call to css.php for example.

Perhaps some sort of caching system that reads a 404 error and caches a 404 error page for a short time rather than returning then passing the data to vBulletin and waiting for a real page to be generated?

I'm kind of grasping at straws here... Are there any PHP errors in the error logs when this happens?