I had two GeForce FX 5500 / 256MB DDR / Video Cards on my PC. A PCI and an AGP. The AGP died. What happened?

I wasn't overclocked, fans were clean. Using Win Xp, P4@1.8g on socket 478 ECS MB, a generic soundblaster from Walmart as were the 2 vid cards. Linksys wireless nic. I just get vertcal lines from the AGP at boot. I cannot get into Windows with the AGP onboard using PCI as default display. a hot spot developes on the AGP card when I try this. I don't have another machine to test the card on in case it is the MB causing the problem. I did have a different monitor on the AGP as I have no web access at home and go to a friends house every month or so to update. When I got home 6/8/2006 the AGP would not work. No extreme vibration during trip, no moisture, inspection revealed no loose cards or cables. I never updated bios or drivers. Forceware 7700 I think. I swapped cards in and out between just the 2 listed, changed bios settings for the cards, nothing worked. It would be nice to get the card working but am more concerned with what happened as I plan to use dual monitors again.