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@sonic.net      510 536 1443    510 282 0869
If simplicity worked, the world would be overrun with insects.