So I noticed my ClamAV database wasn't being updated on the new server. Okay, I forgot to put the freshclam line in clamav's crontab. That was a quick fix.

Except it wasn't. The line was gone. The crontab file was empty. Maybe I forgot to save it before I did something else and rebooted the box. So I put it in again. Saved it this time.

And I'm still getting "outdated database" warnings. Huh?

It turns out, crontab was quietly dropping the changes on the floor. Creating a .vimrc in /root with the line "set backupcopy=yes" fixed everything.

Why this is relevant, I don't know.