No such luck with the CPU. Arrived today, switched the chip out, still not working (in fact, now the computer isn't even posting anymore, which I could at least get it to do occasionally before freezing with the old CPU). I'll get another look at it tomorrow, but it looks like a new motherboard is now in order.
So, long story short, I'm still out of commision, and will probably buy myself a new computer, piece-by-piece, until I finally replace the part that was causing the problem.