I don't know if this has been reported or not, but there seems to be a problem with gv's falling into invisible rifts in the terrain, whereby the vehicle's track/wheels accelerate to extremely high speeds while the vehicle itself just spins in circles half in, half out of the terrain. The only way out of the situation, that I have found, is alt f4. This happens to all vehicles on different areas of the map. I have heard several different people mention this happening to them the few times that I have been online.
If more specific locations or information is needed I'll be happy to go find one of these 'rifts'.
Otherwise the game runs as well as can be expected on my old GF2 MX card, AMD 1.67GHz, 512mb system running XP.