As you can see, savefs fails and seems to suggest you can't talk or get an answer from client. This may suggest your XP has firewall configured blocking communication back to server/client.

Try following from server:
echo print | nsradmin -p 390113 -i - -s client.domain.com

and

rpcinfo -p client.domain.com

Output of "echo print | nsradmin -p 390113 -i - -s client.domain.com":

type: NSRLA;
name: client.domain.com;
NW instance info operations: ;
NW instance info file: ;
installed products: NetWorker 7.3.3.Build.510;
version: "EMC NetWorker 7.3.3.Build.510 ";
servers: server.domain.com;
auth methods: "0.0.0.0/0,nsrauth/oldauth";
administrator: \
"group=Administrators,host=client.domain.com",
"group=Administrators,host=localhost",
"isroot,host=server.domain.com";
kernel arch: INTEL_PENTIUM;
machine type: desktop;
OS: Windows XP 5.1;
NetWorker version: 7.3.3.Build.510;
client OS type: Windows NT Workstation on Intel;
CPUs: 2;
MB used: 20465;
IP address: 172.21.7.3;


Output of "rpcinfo -p client.domain.com":
program vers proto port
100000 2 tcp 7938 portmapper
100000 2 udp 7938 portmapper
390436 1 tcp 8190
390435 1 tcp 8371
390113 1 tcp 7937 nsrexec

Make sure your client is called client.domain.com. Then check if nslookup on it will give you 172.21.7.3 and the other way around. Check also short name and make sure it is on alias list of client.

As it works in one direction, do start backup again and go to client. Check with task manager if you see thw save or savefs. In case you have VSS licenses, try to force NW not to use it.

The client hostname is correct, both short and long versions, and nslookup works both ways, using IP or using hostname. Both short and long hostnames are listed in the alias field of the client config in NW. I also added the hostname and IPs to the hosts file, just to cover all the bases.

We don't have any VSS licenses, and I'm not sure how to force NW not to use them, but since we don't have any that shouldn't matter, right?

The client is currently offline; I will test another backup and check Task Manager when it's back (likely tomorrow).

Yes, VSS in that case should not be used. I suspect it hangs at savefs part... in case you use saveset All you would see in group details contacting clients and All not being resolved to savesets on that machine. One thing to try also is to install backup server on that client (eval), create disk device and try same savset backup.. if that works it means issue is not on client but rather on server or path from clint to server (eg. network routing, firewall, some problematic NIC parameter like oflloading, etc).