Frame-rate and options isue

[Loeka]

I have played L4D2 for a very long time but I have never experienced what I am now going trought. Whenever I start L4D2 the game seems to reset all my video- and sound settings to the default. These default settings lag on my system, so I change them a bit. Then, after playing for 10 munites, a random framedrop comes in. I get about 3 frames per second, for no reason. Does anybody else have this problem, or did anybody fix it? I would like to hear.