I eventually got the debug working, and the problems dissapeared in a jiffy!
Basically add the line DEBUG_LOGIN=2
to your authdaemonrc config file. Also add *.debug /var/log/debug
to /etc/syslog.conf even if there is one saying *.=debug
I set ISPC to use maildir and created some sites.
My system is ubuntu 6.10 [following falko's advice] and ISPC 2.2.9