Go Back to basics. I know it is a pain, but it will work.
1.) Make a backup.
2.) Shut off your hooks/plugin system. (you may have not deleted your MOD's correctly).
3.) Create a new default style or master style (use tools.php) if you think you accidently modified it.
4.) Clear vbulletins cache from the maintenance section. If you are using external CSS files, make sure they are regenerated.
5.) Clear your browser cache, before rechecking.