After removing the suspect drive and suffering more crashes, all while i was trying to transfer files to and from drives, i determined that the culprit was the goddamned primary 80-wire UDMA cable.
I ended up moving some files instead of copying them from drive to drive, so in returning to my original drive, i was missing some stuff, most importantly some log files; syslogd (the program that writes system logs) is still stupid in that if it tries to log to a file and realizes that it's not there, it will fail with a whine instead of creating the file. This is indisputably broken behavior and i don't know why we put up with it this way.
The worst of all this was that i blew away my mail server configuration. Not a big deal, though, just a moment of panic. There's also some brokenness in my news spool, but i think that'll sort itself out after tonight's expiration run.