I've been wondering about phenom stability. I've kept an eye on the motherboard reviews at Bit-Tech and not one AMD system has passed their stability testing 100% with a phenom. Most boards reviewed with an X2 passed back in the day, as do most intel systems now.
A couple of things, I suppose.
Consumer Phenom-based systems are - from my experience - pretty much fine: my father-in-law uses his until the cows come home playing Supreme Commander. True, he's not playing it through the night whilst Prime-ing or whatever, but it works for him.
Likewise, colloquial stories on the internet about Phenom-based systems not working seem to be in the vast minority... most of the ones I've read talk about how glassy smooth the systems described seem to be.
We also have Barcelona doing pretty well in the server market, and I'm taking a guess IT bods don't really want their servers falling over when lunch-break at University comes around.
On the other hand, I trust Bit-Tech and their reviews more than most on the internet and so there is reasonable cause for concern if they report AM2+ motherboards not being stable when put through the hypothetical mill.
What seems to be the case to me is that AMD were so secretive about what Phenom required to work to its potential that it caught motherboard makers off-guard... potentially indicated by the motherboards Anandtech have tested which go pop! when faced with a Phenom.
This has long been a criticism of motherboard makers for AMD-based systems: that they are somewhat lacking when compared to their Intel-based equivalents... digital power management being one voiced regularly over at XtremeSystems.
Long and the short? I would say the OP's motherboard may not be up to the job, or that case airflow might not be sufficient to cool the MOSFETs down sufficiently.
Of all the problems I've had with my computers over the years, only two have not been caused by me... either through screwing with the configuration, or through the use of unsuitable components. Or not attaching said components (i.e. waterblocks) properly.