Sounds to me like you have an SLI setup. From what I remember the 680i was a bit buggy anyway.
What I would do is remove everything to a minimalist setup. 1 stick of ram, a low power (or pci slot video card) if you have one (if not back it doen to a single PCI-e card, no drives except the boot harddrive, etc.
Start with that. Reboot and change or add components one at a time to isolate the problem.
Inspect the board for bulging or leaking capacitors. Also, remove and reseat every card and connection. If you have an overclock or aggressive ram setting, undo them back to stock.
What I would do is remove everything to a minimalist setup. 1 stick of ram, a low power (or pci slot video card) if you have one (if not back it doen to a single PCI-e card, no drives except the boot harddrive, etc.
Start with that. Reboot and change or add components one at a time to isolate the problem.
Inspect the board for bulging or leaking capacitors. Also, remove and reseat every card and connection. If you have an overclock or aggressive ram setting, undo them back to stock.