I had the 861 running for two hours last night and it worked perfectly. Not a single shut-down.
Anyway, I'm in touch with my dealer (who I'm sure is reading here as well

) and I have several options now. Measuring the current power supply, which will probably lead to the procedure you suggested George. Or, since it is still under warranty, having it send back to my dealer and have it repaired there. And lastly, having it send back to my dealer, have it repaired and upgraded to v8 at the same time.
In any case, I'll keep an eye on it over the weekend and see if it shuts down again. I'll also think a little about the v8 upgrade over the weekend, so I can make a decision on that. While I wouldn't need the ID29 card, I'd certainly benefit from the new PSU and SL card.
I'll keep you guys updated.