FWIW, my recently ordered Crucial Corsair memory (two pairs of 512MB sticks for a total of 2GB of memory) was all bad. I'd suggest you run Memtest first thing.

Hmm, I bought Corsair, too, so I'd like to take your advice do an extensive memory test. I'm aware that the cursory RAM test the BIOS does at bootup can't show all possible kinds of memory errors, but I've never bothered to do a full test using third-party software. What's the best "free" memory test utility out there?