Just a quick answer aside from card upgrade issues Dave.
Could actually be that the card is
ok and the system is failing due to insufficient power delivery. You my have never maxed it out before!
Do you have an addition power connector that goes to the card itself? Most PCI-e cards do require and additional power input
400w sounds minimal but could be enough if you disconnect peripheral devices to reduce the overall load
http://archive.atomicmpc.com.au/foru...s=2&c=7&t=9354