proftpd does not start after ip-adress updates

[fuban]

hi,

i setup my ispconfig server with a local ip adress, all worked fine.

now i updated my network-configuration and changed the local ip (192.168.0.50) to the public one - everything is working fine but the proftpd does not start up and the boot process stops.
when i boot the machine with the recovery console i see that ispconfig updated the config file for proftpd. looks right.

also when i try to start proftpd with degug information i get no error messages.

any ideas?
thanks, fabian