Posted one thread below you. USE THE F*CKING SEARCH BUTTON.
I've seen something around here about clearing up your hax_ cvars in some file... i'm gonna go look for it
EDIT: AHA! i found it!
1. go to: \Call of Duty 4\players\profiles\profil-name
2. open the config_mp.cfg with wordpad or an other texteditor.
3. delete everything that starts with hax_.
4. have fun!