[Serusers] Problem with MS Messenger and SER 8.12 - "Service unavailable"

I am running SER 8.12 (with radius modules) on a Redhat Linux ES 3.0 system. My client is MS Windows Messenger 4.72. I start MS Windows Messenger and quickly receive the following message: "Signing in to Communications Service failed because the service is temporarily unavailable." I have attached the ngrep from the server, and also a packet capture at the client workstation running MS Win Messenger. I am registering as morriss(a)orau.gov, and I believe the coxT(a)orau.gov is showing up because this person is one my contact list. Scott Morris Enterprise Network Engineer DOE - ORAU / ORISE 865-576-4672