There are many complaints about BF3 freezing after a few minutes, usually during loading/saving or in the middle of a mission.
I have not seen any solution posted any where. There were suggestions that RemoveWAT used on Windows 7 may be the culprit. But that does not apply to this problem.
Actually, the solution is very simple. In BF3, just go to Options –> Game Play and disable PunkBuster. That’s it!