Happened to this guy before: http://www.quakelive.com/forum/showt...mapping-issues. (I can check IP of that guy, he's from Comcast)

Sounds the same: http://h30434.www3.hp.com/t5/Desktop...en/td-p/674859

To sum up the above thread:
- Comcast provides some security solution to its customers.
- Part of that solution is a program called GuardedID. It's a "keylogger protection" solution (Cat guessed it right).
- Uninstall that crap and your problems go away :)