Faulty Graphics card or something else ?

A friend of mine has a BFG 6800gt OC(factory overclocked) AGP in a system with 2gig of ddr2 ram and an icute 400w psu. Had been running fine until 1 day when he loaded up World of Warcraft it took 2mins to load up instead of 10 -20s. Once in the game seems to run fine, other times it will be running fine then computer crashes and restarts.

Only seems to happen in games, windows runs fine.

I thought it was probably a faulty or overheating graphics card or faulty psu. Dosen't have a second AGP card to test with.

What are your guys thoughts ?
Does it sound like a faulty graphics card ?
Could a faulty graphics card cause slower loading times ?