just removed a card to see how it runs.
edit: running fine with 2 cards, not sure why its gving issues all of a sudden with 3? i added a fan about 4days ago but was running no probs till a few hours ago.
Your PSU can't handel three HD6950. You need a bigger PSU, 900W+.
haha This one maybe but got a number of these rigs running for months not a hitch they maybe draw on a bad day 200w MAYBE! but yes it is this psu, bought it used so guessing its had its day.