My server and websites are back up, hooray. It was interesting doing the rebuild from a couple hundred miles away, but thanks to knoppix (or whatever other bootable CD your friendly hosting provider supplies) it wasn't too painful.
So the result is: no more email hosting for me, no sirree. I don't know if that was the problem or if it was ssh as Matt suggested, or maybe TWiki. But email is a PITA anyway, and since gmail offers POP access it seems a pretty simple choice.
As a result of the server rebuild the site is now running on Postgres 8.0.3, previously it was 7.3.x (I think). And I noticed tonight an error very similar to this one reported a few months ago by a CDBI user -- something about a prepared statement 'dbdpg_150' already existing.
What's weird is this: I'm not using cached queries. At all. So I'm thinking the driver was trying to do some optimization under the covers, I dunno. I upgraded to DBD::Pg 1.43_01 to see if that'll help. More soon...