Fail2ban (without iptables) doesn't work, why?

[MET]

My externally hosted vserver runs with Debian lenny stable. Fail2ban 0.8.3 (and iptables) have been installed with the package-manager. The intention is to use fail2ban with the messages-file from asterisk, i.e. without iptables. The configuration files for fail2ban are according this howto.

When I start fail2ban with
/etc/init.d/fail2ban start
no further information is given, so I thought it would work. Later I questioned whether it would require beforehand a
/etc/init.d/fail2ban reload
or a
/etc/init.d/fail2ban restart
and in both of these cases I obtain each time the result "failed!"

How could I find out what is going wrong?

Note: I'm not very familiar with Linux, I only use it in the context of the asterisk.