Update: Tried disconnecting Crossfire bridges and still have the same problem.
Advice please? Anybody who can fix this for me gets .5 BTC
I think you should try diablo miner.
Also what is your CPU usage like while you are mining?
I have not tried mining with multiple cards but I might be able to help. Have you tried different miners in guiminer and what kernel are you using? I find the phatk kernels with polcbm to be vastly superior to my 6950 which is a 6970 with locked cores but that is only with one.
One more thing to try is to reduce the aggression on the mining as this may be causing a limitation
[EDIT]
Also try just running 2 cards to see if you have the same problem. I would assume you have a 1000W P/S you are powering these cards with. I dont think that would be a problem though as likely the power supply would blow up if it were overloaded.
Honestly, I'm exhausted at the moment (haven't sat down in 18 hours) and I don't really know anything about kernals, aggression settings, and have never experimented with other miner programs.
I have a 1050W PSU.
If you have any other advice, leave it here and I will check it tomorrow or Friday when I get a chance. Bounty is still on the table and it may be increased if this is really a pain in the ass.
Thanks so far
(BTW, an explanation of kernals and aggression would be awesome!)