Flaky computer

My machine refused to boot a few days ago (as posted here). After blowing with compressed air, it seemed OK for a while. Then it froze up hard 3 or 4 times. I tried Memtest on it, which refused to boot. Then it started just beeping and refusing to boot. I pulled a DIMM, then it booted. Got the new version of Memtest, it worked. Put the RAM back in, Memtest said all was well. It seems stable now.

It's possible the RAM was just not seated properly. Or maybe I jarred something else while futzing in there. We'll see. It hasn't acted up today yet.