Ok, I think I found the problem for sure now.
At first I thought it was memory, then the tests on individual sticks came back clear, and a subsequent test with all the DIMMS in place did as well.
That said, the game runs fine as long as I am not in Org too long or part of a 40 man raid. It crashed three times on me in Ony's lair last night after going days without crashing. On the last crash, I went into my BIOS and looked at the PC health stats...my power supply was fluctuating more than I had ever seen before on all the voltage rails, and I actually watched the +5v rail drop to 0.00V on several occassions. The power supply is a 500 Watt supply, but is over 2 years old (which shouldn't make a difference), but it is obviously going bad.
So...it appears to be power supply related, and a new one has been ordered and on the way.