One of the four drives in the RAID array lunched itself a while back, and I received a replacement this afternoon. Fitting it was a snap, the Buffalo Terastation Pro uses quick release drive caddies, so all I had to do was unscrew and replace the drive. The folk at RL Supplies had the right drives, and they delivered the replacement pretty quickly.
(Actually, the first thing I had to do was find the key to open the drive bay door, which in my usual efficiency I had "filed". Once that panic was over I could get to work.)
Once it was in I powered up the NAS to discover that the crash had also lunched its firmware. Luckily I could download some replacement code, and fire it off at the box. Of course the firmware updater needed me to turn of the firewall on my desktop PC so it could actually see the NAS. Still, updating the firmware was pretty straight forward, so I didn't have to much to worry about there.
Reflashed, it booted, and I could finally see the web UI. The three remaining disks were OK, and all that remained was clicking the "rebuild array" button. Oh, and waiting. And waiting. It's looking as though the process will take about ten hours. At least I was running RAID 5 and could do the restore, so waiting for the data to come back is really not too much of a hassle compared to not having anything.
And then I'll be able to get back to the house music collection - as I've ripped everything we have and stored it on the NAS. And, err, the wedding photos.