Problems with OCing my 9000

Well I got an ABit KT7A-Raid system with latest BIOS and win XP Pro. I try to overclock my vid card, a Saphire Radeon 9000, with powerstrip. If I even try to overclock the memory by a couple MHz, the system reboots after applying changes. What can be causing this? Should I add more I/O Voltage? Or do I need to add cooling to the card?

Note that it also does the same with GPU speed, although with a bigger leeway.

You have to update the video card bios to be able to overclock to much higher speeds.. www.guru3d.com has bios and flasher..

Thanks. I'll try