I've had it. The chip upgrade was a bust. To test my theory that it was the over-endowed muscle that was killing my server daily, I quickly disassembled and reassembled humpty-dumpty in less than 10-minutes using the old Sempron stock chip.
Guess what, Voila! No more reboots, no more hangs, no more shutdowns. The memory upgrade was sufficient enough to get everything up to speed. So yeah, I guess HP was right in allowing the memory upgrade but not the chip as it is sufficient to run the standard gamut of applications intended. Of course, if you're wanting to use the MediaSmart for some super computing then maybe its best to invest in some high power fans, extra cooling, or better yet building your own instead of using the weakly ventilated version.