Can't resolve mx for cder.fda.gov

[Frank.C.Hui at ap.pnu.com]

We have an external and internal nameservers.  The internal server will forward
any external query to our external server sitting on our DMZ.  Lately, a strange
thing is happening to our external server.  Here is what we see:

Both servers are Solaris 2.6 running Bind 8.2.2 with level patch5.  Our internet
mail gateway  resolves using our internal nameserver for routing.  The past 2
weeks, the internal server failed to resolve the mx record for cder.fda.gov
twice.   What stumped me is that this is only domain our  nameserver was having
trouble with.  When I used dig to query for the mx record for cder.fda.gov, it
hanged and then timed out.  When I specified with the no recursion option, dig
returned the ns record for fda.gov, but no mx record.   My solution for both
times was to reboot my external nameserver.   BTW, I've checked my firewall's
rule base and everything seemed normal.

Had anybody experienced anything like this before?

Thanks
Frank Hui
Systems Engineer
Pharmacia Corp