FW: Authoritative answer "no data" 50% of the time

[admjcd]

hi all,
 
   I am a messaging administrator having a intermittent (50% of every day for a few hour intervals)  problem sending to a few sub domains at army.mil.  One of which is lee.army.mil.  Our DNS server is the only DNS server we can query behind our firewall.  It some-times gives the correct response when looking up the mx records for these domains.  and the other 50% of the time it returns this response:  
 
Query:All records (ALL):lee.army.mil
Authoritative Answer
Server has no data for this query
 
However; if I direct dial the Internet and query any other DNS server I always (99.8%) get the correct response.  especially if I query all the NS servers listed for these domains. ns01.army.mil ns02.army.mil and ns03.army.mil.  
 
We are using Bind on Unix with the latest version.  Our DNS- Unix admin is new and did not set up and configure the server server    My questions are:
 
1.  Is there a config file that can be listing an old bogus or (lame) server as authoritative for these domains that would respond back with an incorrect answer?  What could make another server believe it is Authoritative for another domain if it is not?
2.  What does it mean when a resolver receives an authoritative answer from a DNS server?   
 3. is there a trouble shooting utility (debug or dig)  that could tell me where this answer is coming from, or where our server is getting this answer?  something like trace-route for DNS queries?
4.  Any other ideas about how to isolate this issue? 
 
thanks in advanced!!
 
-John