netbsd-5 recurring named crash

[Chris Ross <cross+netbsd%distal.com@localhost>]

 I am running the stock named on a netbsd-5 system from mid July 
sources.  I have been seeing it crash and dump core repeatedly.  It 
tends to run for a few days, then fail.  The last one, as may've 
previous, yielded the following assertion failure to syslog before dumping:

Aug 23 00:48:49 server named[1946]: 
/data/NetBSD/src-5/dist/bind/lib/dns/rbtdb.c:1441: REQUIRE(prev > 0) failed
Aug 23 00:48:49 server named[1946]: exiting (due to assertion failure)

 If anyone has any suggestions what I might be doing to provoke this, 
I'd be happy to hear it.

 Thanks.

                          - Chris