Odd issue

[Bateluer]

This problem just started occuring after I purchased and installed my 6800 Series graphics card. And it only occurs at random, doesn't have a pattern that I can see. When I reboot my system, it goes through its normal POST routine and loads WinXP Pro. After the logon information is entered, it starts loading the Systray items. During that load process the system will spontaneously reboot. Sometimes it loops 2 or 3 times before stabilizing in windows. The problem occurs on both Asus's drivers, which have a rev of 61.21, and Nvidia's 61.77 drivers, which I am currently running.

System specs
2.4C P4
Asus P4P800 Deluxe
1GB Corsair DDR400
Asus V9999 GE
Tru430 PSU
SB Audigy LS

At first I thought power was the issue, however, I recently bumped my PSU from a 350 to an Antec TRU430, and the reboot loop still occurs at random. My next thought was a heat issue, however Motherboard Monitor never reports the CPU temp higher than 47^C(After 2hours of Doom3), and Asus SmartDoctor never reports the Vidcard temp as higher than 67^C. According to several 6800 owners, thats pretty normal full load temp for the 6800 series cards. On the off hand chance it was a mobo issue, I just flashed my bios to 1017, the latest Asus has available and updated all the chipset drivers with the most recent editions.

Any ideas?

Edit - My next step would likely be to pull out the V9999 GE card and put my old 9600 Pro back in. However, thats going to require some work removing the Nvidia drivers and installing the ATI drivers.
If it does turn out that the Asus card is defective, I've got 30 days to return it for a refund/replace.