PG Server Crash

OK, I got a nasty surprise today. The server threw everybody out of the pool and logged this:

10.224.12.4(52763) idle: pthread_mutex_lock.c:80: __pthread_mutex_lock: Assertion `mutex->__data.__owner == 0' failed.
:4d45a006.78ec:2011-03-07 11:57:45.316 EST:LOG: server process (PID 21298) was terminated by signal 6: Aborted
:4d45a006.78ec:2011-03-07 11:57:45.316 EST:LOG: terminating any other active server processes

It then stopped all the backends, restarted, recovered and worked fine for the rest of the day.

The particulars:

SLES 10
PG 8.4.1
8-way Intel Xeon E5345 @ 2.33GHz
32 GB RAM

max_connections = 1500
shared_buffers = 1536MB
work_mem = 32MB
maintenance_work_mem = 256MB
checkpoint_segments = 2048
effective_cache_size = 20GB
effective_io_concurrency = 6
random_page_cost = 2.0

This server has been rock solid running 8.4.1 for over a year. It has Slony replicating to another mirror image server that has not had any problems whatsoever.

Any ideas?

Thanks in advance for all your help, and especially for the amazing database software!

Regards,

Bob Lunney