I don't know if this is the correct forum area but I didn't know where to put this. Recently there was an update to perl 5.10 Using apt in debian the perl modules are not updated when installed via CPAN. This leads to a non-working spamassassin and missing perl modules that seem to be requested by the ispconfig installation. If ispconfig is already installed you won't notice this problem I think. Maybe ispconfig could check for some needed perl modules and send a warning if they are missing?
Just install the perl modukles via apt as described in the perfect setup guide, then they will get updated automatically.