Yes, it's important that name resolution is working in both directions so this needs to be resolved. All you need to do is add an entry for the media server in sys:\etc\hosts.
You are backing up (and making selections) via Remote Selections-->NetWare Agents yes? If so, the agent should be used...
You are also using an old agent which could be a problem - depending on which SP/Hotfix level you are at on your media server. Here's the latest NetWare agent - but note the minimum requirements on your media server before installing:
http://support.veritas.com/docs/282302