MailScanner keeps restarting, mails are kept on hold

[forum]

Hi,
I am using MailScanner on a Ubuntu Dapper server (running, productive 
system, therefore older) and everything was working fine before I did an 
apt-get upgrade. Now MailScanner keeps restarting with these log entries:

timestamp servername MailScanner[##]: Using locktype = flock
timestamp servername MailScanner[##]: MailScanner E-Mail Virus Scanner 
version 4.46.2 starting...
timestamp servername MailScanner[##]: Read 676 hostnames from the 
phishing whitelist

Apparently this could result from an unusable bayes database for 
SpamAssassin but I have rebuilt that and cleared (just to be sure) it. I 
have re-installed MailScanner and also tried to install a newer version, 
which failed dismally, as a lot of dependencies are not met with the 
standard Dapper packages (and I couldn't backport them).

How can I resolve this issue without too much trouble/time?

juro