OperationalError: FATAL: lock AccessShareLock on object 0/1260/0 is already

This seems to be bug month for my client. Now there are seeing periods
where all new connections fail immediately with the error:

FATAL: lock AccessShareLock on object 0/1260/0 is already held

This happens on postgresql 8.4.7 on a large (512GB, 32 core) system that has
been up for months. It started happening sporadicly a few days ago. It will
do this for a period of several minutes to an hour and then go back to
normal for hours or days.

One complete failing session out of several hundred around that time:
-----------------
2011-08-09 00:01:04.446 8823 [unknown] [unknown] LOG: connection received: host=op05.xxx port=34067
2011-08-09 00:01:04.446 8823 c77 apps LOG: connection authorized: user=apps database=c77
2011-08-09 00:01:04.449 8823 c77 apps FATAL: lock AccessShareLock on object 0/1260/0 is already held
------------------

What can I do to help track this down?

-dg

--
David Gould daveg(at)sonic(dot)net 510 536 1443 510 282 0869
If simplicity worked, the world would be overrun with insects.