Ghostrider had been shutting down in an inexplicable manner every day or two since I’d put the new hard drive in. I finally took the time to install MBM5 on it to check it out and it confirmed what the problem was. The CPU temperature was too high; this is due to the fact that I slowed down the variable-speed case fan when I put the hard drive in. Mistake!

I’ve shut the server down and will fix this when I get home later today. ICYG and my FTP server will be back up this evening.

Update: Apparently it was more than just that fan – I took off the CPU’s heat sink and there was little thermal conductor left between it and the top of the processor. So I cleaned out all the fans and heat sinks and put some thermal paste between the heat sink and the CPU. Things are cooler. I’m assuming there’s no permanent damage, since this was really the first sign anything was wrong.