Since I still run my own mail infrastructure, I also run anti-spam and anti-virus on it.
Today I noticed that free space on my server running lenny was ALOT less then usual. Turned out that clamav was crashing all the time causing lots of temporary files in /var/lib/amavis/tmp.
An upgrade of clamav also stopped the crashes.
While at it I also disabled quarantining virus mails, I never had to retrieve any mail out of there anyway...