broken threading

I had to rebuild a month's worth of archives (we had to change some ad
code in a header file).

Why would messages not thread after a rebuild? I followed the following
procedure:
- delete .monarch.db and index.html
- inside the directory, run mha-dbrecover
- run mhonarc -editidx -treverse -reverse -rcfile /path/to/rcsfile

Any input?

- John Hogan