Error after postfix upgrade

[remeryspam at cfl.rr.com]

I have been running an Ubuntu 6.06 LTS server for the past 6 months with postfix and mailscanner installed from the repositories. Everything has been working great!

Yesterday, I ran the updates on the server, which updated postfix from 2.2.10-1ubuntu0.1 to 2.4.5-3build1~dapper1 (mailscanner is at 4.46.2-3). After the update, mail wasn't being delivered and I noticed this message in the logs every time mailscanner runs:

postfix: Process did not exit cleanly, returned 255 with signal 0

If I run postfix without mailscanner, it runs without logging errors. I switched mailscanner to run with debug = yes, and ran check_mailscanner, and got this message:

Can't call method "DropFromBatch" on unblessed reference at /usr/share/MailScanner/MailScanner/Postfix.pm line 332.

The code there is:

# If the data offset is 0 then Postfix definitely hasn't finished
# writing the message.
unless ($DataOffset+0 > 10) { # 10 == arbitrarily small number
   $message->DropFromBatch();
   return 0;
}

I am a programmer, but am not at all familiar with Perl, so am not sure what the problem is.

Any thoughts/advice?

Thanks in advance,
Rick