What resolution is is your screen running at ?
Can you download GPUZ and see what your gpu temperature is? Could be over-heating.
I'm running it at 1440x900, but it's not like it's going to be overloaded on the bios and boot screens, is it?
The card is now idling at 46°C, which does seem a bit on the hot side.
For the record (somehow I managed to not include this) it's an XFX 5850.