#RedCarDriver :
Sounds like you might be running out of RAM.
I strongly recommend removing any high-definition texture packs if you have them, and trying to minimize the amount of time you have the game open. You may also want to download SlrrExhaustive Bits and use that, because it has memory management functions not present in the main game. (If you're already running SlrrExhaustive, you don't need SlrrExhaustive Bits.)
Hmm, I'm using the game mostly as it came, only thing I added where few wheels, steering wheels, one car and engine and I never had issues of this kind before, but I've just tried with SlrrExhaustive and it worked perfectly, though I prefer the mouse cursor that comes in the pack by Miegalius, but gotta pay that small price if I wanna play the game with no problems xD
