I have a sapphire all in wonder 9800 pro graphic card and had a similar problem since i upgraded my drivers to cat 5.6 with ccc. The recovery of vpu and crash to desktop while playing everquest 2.
I looked at several forums regarding this but didnt find a solution. Some people suggested that i should check my which my system temperature.I have overclocked my graphic card on numerous occasions and didnt had any problems what so ever so i ruled out the possibility of my vga getting overheated.
After doing some tinkering with the graphic card, i found out that the problem lies with the catalyst control centre. The ccc uses dot net framework 1.1. The .net framework usually (for some unknown reason) stops responding to the ccc commands and eventually causes ur graphic card to reset. One of the solution is to use catalyst drivers w/o ccc or use and older driver. Try using cat 5.4, im running this at the moment and have not had the same problem again. If the problem persists then check your power requirements and system temperature which i highly doubt is the root of the problem.