fps lag!

Hi there lads,

I recently switched over from a GT160 (broken) to a HD5750. For some reason all games run fine, except ET. I never used to have this before and I already tried shitloads of settings in the catalyst center but im getting fps lags.

Im stable 125fps till some strikes / nades explode and then my fps drops to 100/90 fps while my mouse just stops moving in between the fps drops, still moves but its really stop move stop move stop move. Its not that much of a hassle in 5vs5 but its driving me insane when playing big pubs.

I guess some other oldfag had this problem before, so i hope by posting here i might get a normal decent reply, maybe even some help!

already tried
- omega drivers
- stock drivers
- checked all obvious fps drainers in settings, got everything on performance except mipmapping at quality
- catalyst ai on/off whatever
- pb on/off
- pbprior ET= highest / high / normal
- driver cleaner

Plz help me cause borderlands is getting boring after playing it one week.

edit: nvm, just reinstalled my old gt8600