[Dovecot] antispam plugin problem with dspam

[Harlan Stenn]

I'm trying to use the dovecot antispam plugin with dspam.

I'm running dovecot 1.1.2.

Using thunderbird and IMAP, when I drag a spam message from the inbox
into the SPAM folder, I get a popup saying "The current command did not
succeed.  The mail server responded: antispam signature not found.

When I look at the message in the maildir folder, I see the dspam
signature both in the header of the message and at the end of the body.

What's a good way to debug this situation and figure things out?  I'm
not seeing anything in any log files, and I'm not seeing much in the way
of debug capability in the dovecot antispam plugin.

Harlan