Mailscanner hangs after a while

[murat at mems.eee.metu.edu.tr]

Dear all,
I have recently installed mailscanner on postfix by following the nice
tutorial on debian-administration.org:
http://www.debian-administration.org/articles/172 (Secure Spam/Virus
filtering system with Debian and MailScanner).

I recently recognized that, Mailscanner works well for a while, and then
does not scan the mails in the queue.  After I restart the mailscanner, it
works well again for a while.  There is nothing related to this in the log
files. Everything seems to be working without errors.

How can I solve this problem? My web search says that there are other
people facing the same problem, but I could not found any good response to
those.

Thanks in advance.

OS: Debian sarge.  Mailscanner version is 4.41.3-2