Even high quality parts have issues from time to time, and an issue between Antec PSUs and Tyan dual Opteron motherboards has cropped up. The Thunder K8S Pro, K8SD Pro, K8W and K8WE, based of the AMD 8000 chipset, show instability when used with the Antec TruePower 2 EPS series power supplies. The problem seems to stem from the PSU not being able to provide consistent voltage, moreso over time. Whether it is a flaw in the design of the motherboard or the power supply isn't known, but non-Antec power supplies are not exhibiting the same effect on the motherboard.
Opteron as a desktop is more common these days, and Antec is one of the premium brands available for PSUs in enthusiasts workstations, so this problem is going to rear its head more often than normal. Antec has not yet released a statement, but considering their good track record and quality products, hopefully the issue will be addressed soon and perhaps the TruePower 2 EPS in the field will be replaced, which often happens in cases such as these.