And, we're up.

Maybe they needed to be prodded? Anyway, the software upgrade didn't work. Here's the text of the email:

It should be up now. We ran into a problem with the migration. The
utility that converts the backup from the 7.5.4 based server to the 8.1.1
server failed. Now that we have a 7.5.4 backup from your server we can
use that to debug the problem with the conversion utilitity. Once we have
that issue resolved, we'll plan another live data migration. This utility
is new to Plesk 8.1.1 and probably has a few kinks that need to be worked
out.