Car parts disappear!

Hi, i have a major problem at the moment. The car parts on my own car and other cars disappear, so all i can see on other cars is the steering wheel and the shadowing of the car, and my own car flickers a lot and you can only see the front axle and the steering wheel. Not sure why this has happened. It was going nicely before, didnt make any mods to the f1graphics.cfg just normal recalibration, had it at a smooth 34fps with quite high graphics levels. My system is:
Celeron 1ghz
GeForce4 MX 440
320mb ram

I'm really puzzled at the moment. Im aware that the processor and graphics card aren't the best available, but the game was working fine, then all of a sudden today, the parts on my car just disappeared and the frame rate bogged down to 16fps. I thought maybe it was a one-off error, so i did a quick race, same problem. Then did a clean remove and reinstalled the game, still the same problem.

Also, i may as well add this in, sorry its dragged on so long. A few days ago, i decided to try PaulBoy's graphics setup, and the same problem happened, so i put the original f1graphics.cfg file back and it worked good again.

If anyone can help me it would be greatly appreciated

Have any other games suddenly gone wrong?

Post a screenshot so people can see exactly what you mean.