I have 2 servers (NW65sp3) servicing a zone. 1 server isn't working

I have found the below issue when using NSLOOKUP from my pc.
I connect to my working server and enter a server name, 'server' - it
resolves ok and gives me a result of server.domain
From a second command prompt I run nslookup and connect to my second dns
server - i try to resolve the same server name 'server' - i get the below
*** dnssvr.domain can't find server: Server failed

But if I type in the full domain name of server.domain then it resolves ok.

I'm totally stuck and this keeps screing up our dns - any help would be
very much appreciated, and just let me know if I can provide any further

Thanks very much in advance..