Domian controller not respond to UDP 389 query

Hi,

We have 3 MS 2003 domian controllers that are not authenticating users. When doing a port query to UDP 389 it fails. As of yet we have not been able to determine what is blocking port 389 for LDAP requests.

I have been working with MS on it but no luck with them yet.

The domain controllers have Exchange 2003 on them along with McAfee Virus Scan and Groupshield for Exchange (groupshield uses Java). We have stopped all McAfee services and still cannot query port 389. Port blocking in Virus Scan is also turned off.

Is there a way I can determine what service or process is using 389 or blocking it. MS wants me to disable all non MS services and reboot the server. I would think there is a better way to just find out what is using 389. We are a 24/7 operation so I'm hoping not to have to down the server like that.

Thank you very much