Shake Appeal said:The game starts out at my usual framerate of ~45-55 (native res, everything on high, v-sync, multicore, antialiasing OFF). Everything plays fine for one, sometimes two, sometimes three maps.
Then at some point during the game it's like a switch has been flipped and my framerate drops to 15 fps and locks there, even if I alt-tab out and in again, change the settings/resolution, whatever. It's always 15 fps, and sometimes 10 during busy scenes. I then have to restart my computer to fix this (if I just quit the game and go back in, it will still be 15 fps).
I think it's the same bug (or a related bug) that this thread discusses:
http://forums.steampowered.com/forums/showthread.php?t=1004211
I had a similar problem. For me, it was due to the graphics card overheating which is strange since graphically superior games don't overheat my card but L4D does :lol