As long as you can reproduce the bug (tell us how to do it, or why it happens), Scawen would know what caused this.
The only thing I can think of that comes close to this is some age-old issue (should be fixed afaik) where the track wouldn't generate completely on loading or something, and sometimes you get some quirky stuff such as in that picture. I've joined quite a few servers and every now and then I see some wierd happenings with invisible terrain and only cars showing, or vice versa.
I don't know if it has anything to do with graphics card drivers, but you might want to try earlier drivers if this issue persists constantly.