I don't use NDMP, we use the Target method, but I believe this will still apply:
Netbackup is not Netware Cluster aware.    You cannot backup the Virtual 
servers, you have to backup
the clustered resources from the physical node that the hosts the resource at 
the time of backup.
In order to access the volume on the physical node you have to turn off 
"cluster awareness" on  the
TSA (TSAFS.NLM i think)  Its been awhile since I've set this up, its done 
through the Netware
Remote Management  Web interface.  Unless you do this  you cannot access the 
clustered resources
from the local host.

Vincent Mase