Just for the record, i would like to share my experience ( i don't think a new thread is needed since it's just my 2 cents ). I had a similar problem...a Voodoo 3 3000 which started to crash on both 3Dmark 99 and 2000.
Given the fact i always suggest to put a fan blowing nearby / or installing one upon on these inadequate heatsinks, i pulled out a perfectly working V3 3000 from a machine, and installed to another machine to test it under games.
Both 3Dmark 99 and 3Dmark2000 started to crash randomly in some tests.
In the end I understood that it was the motherboard, which although apparently stable (I had stressed it well between CPU and RAM without giving errors), still caused the Voodoo 3 to crash in games. ( motherboards were both based on Apollo Pro 133 chipset )