Just an update...I did seem to have issues with stability as I went. Granted there were a string of BSOD that I had. I have no idea what truly happened but I moved everything back to stock on the CPU and GPU and I was fine. I guess its just about finding the perfect balance.
Maybe heats your issue.
This isn't really the very best example but on my i7-930 I have a hyper 212+ cooler and the first time I applied thermal paste it was...crappy. At that time I could barely crack 3.0 ghz before 1) cores broke 80c and 2) my mobo wouldn't post
Once I reseated I got to 4.0ghz with sane cooler no problems stable (I made it 3.5 ghz for everyday use)
Not really sure if that helped what im trying to say is that the heat won't let you overclock and 5850's run pretty hot...