When trying to restart named, you get an error stating that some parameter is not given correctly in a zone file.
It would be a reverse PTR zone file with name something like this:
x.x.x.in-addr.arpa.
Open the zone file using vim , like :
# vim /var/named/run-root/var/xx.xx.xx.in-addr.arpa.db
When you check the file, you can see a mis-configuration in a particular line when compared with other lines. You can easily spot that with your naked eye.
Edit that misconfigured line (check how other lines are written ) and save it and restart named service.
This is a bug which is seen in older versions of Plesk.