Wow, I missed that somehow. Thanks, I'll do that.
I'm also running
Windows Memory Diagnostic (the tool is a bootable 32-bit program you run from CD, so can test 4GB RAM max, but otherwise it works on any system), in the extended tests mode, and it will run 9+ hours while I'm away, so if there is a RAM problem that should find it--I've had it catch problems with a bad stick in the past. If it's useful for anyone else,
Vista (and presumably 7) have a version of this built-in.