It's not unusual for the 2900 to hit in the 90's. My x1950xt hits 92 when OC, and none of the ATI software has a problem with it. If another video card has a problem, you might want to check the PSU connectors, even with a 1000W PSU, it still might be bad. Check to see if anything visibly might be shorting one or two of the cards as well. Trying another monitor will help to narrow the problem down some.