I mailed SW-Soft about this and they supplied a fix, but the fix was to be applied to a different file to what they suggested. I informed them of this so they 'should' in theory be informing customers of the correct file to modify now.
Anyways, here's how to solve the problem on Debian 3.1. This fix has worked for me wonderfully.
In and around line 126 of /etc/init.d/qmail, the line should read:
pidofproc $proccess > /var/run/qmail.pid 2>&1
Restart qmail
Edit /opt/psa/etc/modules/watchdog/monitrc.tpl
Make the following changes:
set daemon 150
#check host qmail with address localhost
check process qmail with pidfile /var/run/qmail.pid
# start = "/opt/psa/admin/bin/mailmng --start-smtpd"
# stop = "/opt/psa/admin/bin/mailmng --stop-smtpd"
start = "/etc/init.d/qmail start"
stop = "/etc/init.d/qmail stop"
# if failed host localhost port 25 protocol smtp with timeout 5
if 5 restarts within 5 cycles then timeout
Restart monit
Give those a try, they worked for me.