Weird slow down issues in Left 4 Dead 2

I'm currently having some frame rate issues in L4D2, in that framerate dips to ~40 every time a new level is loaded (after the safe room).

Upon starting the game, framerate is in the low 200s, but subsequently dips with every new chapter. If I change a video setting (i.e. Anti Aliasing, AA etc), the game "resets" itself, and performance returns.

I have tried the latest Catalyst drivers, but to no avail.

Note: I play at 1680x1050 max in game settings with system in sig.

Thanks for the input!

Im having the same issue with my 4870x2. Apparently its an issue with crossfire / SLI. I hope they patch it soon.

Yup, having the same issue with my SLI setup. I figured it was a driver issue since it used to work fine, nice to hear that it's a problem with the game.

Yeah it's a known issue.. If you ALT-TAB out of the game and go back in after each level load it will correct itself.

hopefully they fix it soon