I upgraded from 2 GB (2x1GB) to 4 GB (2X4GB) of RAM last week. Then, being greedy, I just put all 6 GB of RAM in, and the computer worked great for a few days. Then one morning nothing would happen when I hit the power button. I removed the old memory and just used the new stuff, and the computer started. The next morning, again the thing won't start. No fans blowing, no LEDs are on, etc. On a whim I pull out the new ram and put the old stuff in, and hey it starts.
Until the next day when, again, it wont start. I switch the ram to a different pair of slots and the machine starts. I've memtested both sets of ram and I don't get any errors. So, is this a motherboard or PS problem? I don't really know what my next trouble shooting step should be if the thing doesn't start again.