LDAP AD Connector problem

I am trying to get the AD Connector working for an exchange upgrade, but every time I try it gives an error, about the server not being an exchange server, so I am guessing the problem is LDAP ports are conflicting. I have changed the LDAP connector for Exchange 5.5 to 379 from 389, rebooted but still no joy!

I need the two server talking together so I can join an new exchange 2003 to a 5.5 (current one), all on one domain, then migrate all to 2003 one day.

Does anyone have any ideas please.