DNS queue_run deadlock

Does anyone know what this error means? I've done a bunch of searches, but haven't found anything helpful.

Things will be running fine and then, for no apparent reason, bbtest will start turning yellow and listing the following as an error:

Error output: dns_queue_run deadlock - loops=10

Yet, when I check on the dns servers all is fine and green. Bbtest will go green again a minute or so later, but go yellow again....and so on.

No one has modified bb-hosts today, so it isn't a typo in a DNS name there.

Any ideas?

Martha