Which Dovecot version do you have installed?
I configured saslauthd and dovecot manually.
Saslauthd is not required on a Dovecot system and should not be installed.
Dovecot gets configured automatically by ISPConfig if its a supported Dovecot version (Dovecot 1.x, e.g. Dovecot 1.2). If its dovecot 2, then it is not supported by ISPConfig.