It is likely that there is a failure message in the saveset completion log. To see this press the "group control" button in the nwadmin GUI, highlight the group that you use to backup the NT server then press the "detail" button and look in the "failed save sets" section.
It is likely that the Legato server is trying to backup the NT server and has not got permission to do so or the NT server does not know the details of the Networker server.
Make sure that there are two services ("Networker Remote exec" and "Storage Management"

running on the NT server. These should have been installed when you installed the Networker client software on the NT server.
Make sure that the NT server can ping all the network interfaces of the Networker server. If it can't, add host entries on the NT server for all interfaces.
Make sure that the Networker server's interface names are in the NT client's backup permissions file. This file is INSTALL DRIVE:\WIN32APP\NSR\RES\SERVERS. I would add entries for all the network interface names for the Networker server (if you have more than one).
If you change the hosts or permissions entries, stop and start the two services and start the remote exec service after the storage management service.
Hope this helps