First and foremost, THANK YOU for your help!

Hmm. I actually reverted back to the existing memory when memory from my other PC did not fix the problem. I don’t have any spare memory around. Can you say with certainty it is a bad memory module(s) or MoBo? How might I rule out the motherboard? What’s the best way to test the memory? Presumably I could replace only one of two modules if bad, right?

-ace