named locks up periodically

I've got a FC1 machine with bind 9.2.2.P3-9 acting as an internal zone
name server for an internal network with a forwarder entry as follows:

        forwarders {
                64.59.135.133;
        };

Internal zone forward/reverse lookups are fine (i.e. machinename.LAN where .LAN is the internal top level domain).  External lookups work fine also.  That is, until some unknown time in the future when everything "freezes" in terms of DNS lookup.

i.e. a "host ip" or "host domain" will stall for both local and remote addresses

The only fix it seems is a "service named restart" until the next time it happens.

There is nothing apparent in any of the logs on the system.

Has anybody run into this mysterious lockup problem with named or can suggest any sort of troubleshooting technique I might apply?

Thanks!

Curtis