Using mandrake-cooker, (patched up) XF 4.2 and kernel 2.4.19. But same problem exist on many other distros. I'm not the only one having this problem or wouldn't care so much. Usually I just disable the renderaccel, but like lowering the clock speed it is not very good for performance. It seems to depend a bit how much you have to lower your speed. Fact is the nvdrivers put it much higher than stock nv driver from XFree, card gets to hot with certain stuff, and locks up.
I cannot remember how much I had to lower to stop the crashes. I think it was 5-10, haven't tried it for months. I could try again if it is of any use.