Have no fear Mav is here (heroic music playing in the background).
Okay go into rivatuner - click on the tab power user - ignore teh message that come up.
Look for the Overclocking options click to expand and look for diable internal clock test - all is then well and you can clock till you drop, using RIVA of course.
Good luck......................TEAM EPUK 4EVA!!
Mav