server crash with "process 22821 releasing ProcSignal slot 32, but it contains 0"

I got a crash on a production server this morning following during
very heavy load. This is postgres 9.1.3 on Linux (going to 9.1.4
asap). I didn't catch a core dump it doesn't look like one would help
anyways. Server is virtualized quad on vmware. Here is the log I
have:

2012-06-25 09:07:45 CDT [postgres(at)ysanalysis]: STATEMENT: CREATE
PROCEDURAL LANGUAGE plpgsql;
2012-06-25 09:07:45 CDT [postgres(at)ysanalysis]: ERROR: language
"plpgsql" already exists
2012-06-25 09:07:45 CDT [postgres(at)ysanalysis]: STATEMENT: CREATE
PROCEDURAL LANGUAGE plpgsql;
2012-06-25 09:08:08 CDT [postgres(at)ysanalysis_hes]: LOG: could not
send data to client: Broken pipe
2012-06-25 09:08:10 CDT [postgres(at)ysanalysis_hes]: LOG: unexpected
EOF on client connection
2012-06-25 09:08:10 CDT [postgres(at)ysanalysis_hes]: LOG: process 22821
releasing ProcSignal slot 32, but it contains 0
2012-06-25 09:08:10 CDT [postgres(at)ysanalysis_hes]: LOG: failed to
find proc 0x7f48617e2ab0 in ProcArray
2012-06-25 09:08:20 CDT [postgres(at)ysanalysis]: ERROR: language
"plpgsql" already exists
2012-06-25 09:08:20 CDT [postgres(at)ysanalysis]: STATEMENT: CREATE
PROCEDURAL LANGUAGE plpgsql;
2012-06-25 09:08:21 CDT [postgres(at)ysanalysis]: ERROR: language
"plpgsql" already exists
2012-06-25 09:08:21 CDT [postgres(at)ysanalysis]: STATEMENT: CREATE
PROCEDURAL LANGUAGE plpgsql;
2012-06-25 09:08:24 CDT [postgres(at)ysanalysis_hes]: FATAL: latch already owned
2012-06-25 09:08:24 CDT [(at)]: LOG: server process (PID 23323) exited
with exit code 1
2012-06-25 09:08:24 CDT [(at)]: LOG: terminating any other active server processes
2012-06-25 09:08:24 CDT [postgres(at)postgres]: WARNING: terminating
connection because of crash of another server process
2012-06-25 09:08:24 CDT [postgres(at)postgres]: DETAIL: The postmaster
has commanded this server process to roll back the current transaction
and exit, because another server process exited abnormally and
possibly corrupted shared memory.

The plpgsql errors are expected. The background here is I have four
threads constantly loading small databases in bash and there was one
long running ETL process in the background as well.

merlin