I have started seeing dns failures with the following messages in named.run

Oct 29 08:32:10.000 general: main: critical: mem.c:672:
INSIST(ctx->stats[size].gets > 0) failed
Oct 29 08:32:10.000 general: main: critical: exiting (due to assertion
failure)
Oct 29 08:32:10.000 general: main: critical: exiting (due to assertion
failure)
Oct 29 08:32:10.000 general: main: notice: exiting

Server is NW6.5SP6 with post SP6 patches, and has not had any recent
changes. Named unloading does not seem to corespond to any event
occruing but seems to happen at random and service can be restored by
closing the DNS server screen and restarting named. It seems to take
from a few minutes to some much longer indeterminate amount of time
before it happens again. I do see a few TIDs regardiong the assertion
failure, however all look to be somewhat dated Any suggestions ???

Gus