dns resolution being denied to some servers

[Frothingdog]

I've a wierd problem that I can't figure out.

Our internal DNS server seems to be denying resolution to a few routers on our network and I can't figure out why.

resolv.conf is configured the same on all our routes, and all routers are in the master dns file.

We are onlly having problems with 8 of our routers (out of the 50 or so we are running)

Is there anything that springs to mind that would be causeing the problem?

Here's a snipet from the LOG file of the dns server:
Jul 12 11:53:51 nms named[8862]: client 1.2.3.4#37947: query (cache) 'router47/A/IN' denied
Jul 12 11:53:52 nms named[8862]: client 1.2.3.4#27328: query 'router47.ops.net/A/IN' denied
Jul 12 11:53:52 nms named[8862]: client 1.2.3.4#31182: query (cache) 'router47/A/IN' denied
Jul 12 11:54:11 nms named[8862]: client 1.2.3.10#37059: query (cache) 8.8.8.8.in-addr.arpa/PTR/IN' denied

Totally at a loss here.

Cheers
Morty