Its giving me this message when I try and mine with 2 different cards.  It recognizes them both and works for a while.  But the second card fails even if i under-clock it.  The first GPU works the whole time no problem.  I have NOT modified the Bios of the cards.  When i disable Crossfire GUI miner cant find the second card.
Im running:
Windows XP
750 Watt PWS
2 x 5830 with crossfire enabled (i have 2 monitors if i need to hook them both up. 
         Both GPUs have been tested and work
GUI miner.
Drivers are all up to date.   Im at a loss.  Other posts on similar topics havent been what i needed. 
Thanks!!