Try this:
Ensure that Domain Name Service (DNS) has the forward and reverse lookup for the master server. To check this from a command prompt, use the <install_dir>\VERITAS\Netbackup\bin\bpclntcmd command.
On the client:
bpclntcmd -hn <master server name>
bpclntcmd -ip <ip address of the master>
bpclntcmd -pn
In all scenarios you are supposed to get back the name on master with corresponding ip address, make sure you get right interface back.
On the master server:
bpclntcmd -hn <client name>
bpclntcmd -ip <ip address of the client>
If the test above fails, place an entry for the client on the local hosts file and vice-versa. Placing the client's name in the hosts file will allow the client to resolve its own IP address and name without going to DNS. This file is located under C:\winnt\system32\drivers\etc