Unable to lookup some external domains

[Nick Baronian]

We are running 9.3.0 on some Linux boxes and are currently having
problems performing a successful lookup on two external domain names
(two that we know of).  These two domains had changes yesterday with
their WhoIs listing.  They both are registered with Network Solutions.
 Both changed who their listed domain servers are.

We cannot get an IP back when we do an nslookup from either of our two
DNS servers.  However, we can successfully look up these two domains
outside our environment.  Currently the DNS servers have their
/etc/resolv.conf listing themselves then our AT&T ISP's dns servers,
isn't this the way it should be?  This way it checks itself then goes
out if it needs to.  If we change the /etc/resolv.conf on our dns
servers to only point to an external vendor's servers or our ISP's, we
get a successful lookup.

When I do a dig on these two domains using the third-party's DNS
servers, I get the correct IPs.  Any idea as to why our dns servers
wouldn't be able to get a successful lookup?

We haven't had any changes to DNS for a few days and that was just a
couple zone edits.  Our dns servers are allowing me to lookup our
domains and other domains, such as cnn.com, yahoo and such without any
problem so I don't think it's a problem with the named.conf.

Anyone else run into this problem with domains who have made recent
changes to their DNS servers listed with Network Solutions?

Thanks,
Nick Baronian