Have you done the normal testing?
from the master nslookup <client name>
nslookup <client ip>
nslookup <client ip> do you get the same name back both time.
the from the client
nslookup <master name>
nslookup <master ip>
check that they can see each other.
add entries to host and see if you can connet
if yes then it is dns..
this is the first thing you should test.