After recently crossfiring 2 7970s, I started having issues CoD:MW2 and Mass Effect. Yet other games such as Team Fortress 2 have no trouble at all. While playing Mass Effect my game will frequently freeze, then after awhile my monitors will flash black as if recovering from a display driver crash, and the game will unfreeze. MW2 does the same but much less frequently. Is this perhaps a result of the games stability regarding crossfire, or perhaps that 7970 crossfire recommends a 1050W PSU when I am running it on only 1000W?
Firstly, congratulations on equipping your PC with the most powerful dual GPU configuration out there in the market today.
Don't worry about your PSU (I was running my CrossFire 7970s on a 750W no problems before) and don't worry about disabling ULPS unless you are overclocking.
My advice: ensure you are running latest drivers. I have been using 12.11Beta11 drivers available on the AMD Catalyst driver page for a month and those are the best yet for both stability and performance. Try cleaning the old drivers also before installing the latest drivers. Finally some older games just won't play nice with CrossFire so as suggested disable CrossFire in such scenerios.