DHCP server not authorised

We had an NT4 domain with a DHCP server on W2K which worked fine. After migrating to an W2K domain, the DHCP server event log messages report that it is not authorised to allocate IP addresses although it does. This is still the same when the server is authorised. I’m trying to add a second DHCP server – on a server which is also a DC – but the service refuses to start.