I've been attempting to authenticate to a NW server from a Windows 2003 R2
Enterprise Server but have been unable to because port 524 is not open
according to nmap.

Attached to the same network on the same switch is a 2003 Standard Server
with the same version of the client which can authenticate. In its case
nmap shows port 524 as open.

The readme for client 4.91sp3 says that 2003 Enterprise is supported with
this client version, but it does not specifically mention R2. Does anyone
have any definitive info on whether this client is supported on that OS?