Ok, having a super strange problem...
Have a new setup with 1x 7990. Installed AMD drivers (latest), fired up guiminer. I have this sucessfully installed on 6 other computers, no issues. This is the only one with a 7990, so I'm guessing something there is causing the problem..
When I start-up guiminer, on my 7990, gpu #2 immediately goes to 100% usage. There are no pools on autostartup (or even entered into guiminer, for that matter). No settings yet. Just a fresh install. Shut down guiminer, #2 goes back to 0% usage, so I'm certain it's causing the problem.
Any thoughts??