The comment file got corrupted, so we’re trying to figure out how to fix it. In the meantime, the blog is not currently displaying comments. It appears to be storing the comments, however, so I hope we’ll get it fixed within a few days.
For all those lost souls that might find this through Google, this is a diary of what we did:
0. The problem arose in part because Berkeley DB was used by the MovableType, and the files got corrupted because of a system outage on a weekend. The corruption was not reported by the system, but the comments didn't show in the author/administrative view of the blog.
1. Under a new account we created a new MovableType installation for performing experiments. We tried exporting the old site and importing it in a new one, but not all the relevant information (formatting, lists of authors, access permissions, etc) was transferred.
2. We used db_verify to identify corrupted database files. They were "cured" by db_dump followed by db_load (remove the original file before you recreate it with db_load).
3. While old comments could be seen, new ones couldn't. The corruption was deeper. We decided to attempt migrating the corrupted database to mySQL, hoping that the migration will read most of the good stuff, and the new database will be consistent.
4. The migration script (db2sql) crashed with the insertion error. We manually edited the source code in the DBI.pm file as not to throw an exception when the insertion is not successful, but to simply continue.
5. It seems to work, and comments that were posted in the past days are now visible. Success!
Conclusion: MovableType is too cheap.