One of my 5 servers started having problems connecting to the master server. Upon starting from batch file that had been running fine previously I get this error:

DevOnline: Failed to register server with error 0x00000005 (No challenge value was received from the master server.)
DevOnline: Treating server as private (invite, follow only)

I have the server listed ?bShouldAdvertise=True?bIsDedicated=True
Query ports are posted and opened in firewall.
Windows Server 2003, 4GB RAM, 2Xdual Xzeons, UT3 ver.1.2

Any ideas?