DNS FLIPS

When i do nslookup..i get the below listed messages:

DNS request timed out..
time out was 2 seconds
****cant find server name for the adress xx.xx.xx.xx:
timed out
****default servers are not available
Default server : unknown

Address: xx.xx.xx.xx (which is actually the right ip of
the dns server)

Surprisingly when a ping with the dns name is made i get
replies!!;0)

Whats up?