One possible issue is that the default port for NDMP protocol (TCP 10000) is blocked by intermediate network device.
Overcome by identifying a tcp port that is accessible in either directtion
(master -> remote and remote -> master)
On master backup exec server edit the services file to modify NDMP protocol port, eg
to change to 10001
ndmp 10001/tcp #revised NDMP protocol port
On the remote server do the same and set to the same port.
IMPORTANT if using non default port, must set on both master and remote.
IMPORTANT if using McAfee VScan 8, must disable or modify following access protection
"Prevent remote creation/modification/deletion of anything in the Windows folder and subfolders Action blocked :Write"