After about 30 minutes of playing, my fps will drop down to a shocking 30. And won't rise until I restart the game again, this is strange because I play on low settings, vsync is off. And normally I'm getting around 90-200 fps on multiplayer. Any help? I love this game, but I just can't play it needing to leave the game and restart it.

I guess I should post my specs too.

AMD FX 3.6ghz 8 core.
Radeon 7870 XFX.
8 Gb ram 1600MHz