Delegation issues in bind 9.2.4 on Solaris.

I am having intermittent delegation issues. I have a split zone dns
configuration running Bind 9.2.4 on Solaris 8.

The zone file for domain.com contains ns records for sub.domain.com.
The authoritative server for sub.domain.com is on the same subnet as my
dns server.

The problem is with Bind not following the ns records to query the
authoritative internal dns server and then forwarding the request to
the external dns servers for resolution. The answers that people are
getting is the correct answer for the external dns. This subdomain
handles mail in my company and is causing major issues.

I tried sniffing the ethernet to see if there was any issue on the
network but when this problem happens bind is not even querying the
authoritative server. All I see is it asking the external servers.

I am using named -u named as my startup command. Bind 9.3 core dumps
on my systems.

Any ideas would be appreciated.