I haven't been able to play CoD4 for a month.
Hacking in CoD 4 is (or was, due to my inability to play) out of control. Most importantly de-ranking and playlist locking.
If you join one of these hacked lobbies mistakenly when you're killed you get negative millions of experience.
You leave because you're angry at all of the people with god mode, you go to find another match, but wait, all of the playlists are grayed out, you can't click them, as you have negative experience and are not level 1.
How do I fix it?