diagnosing a db crash - server exit code 2

I am trying to get my head around why I keep getting crashes to my PG 8.3.7 database on CentOS - Linux version 2.6.18-164.el5. There are 3 slightly different (I think) circumstances leading to a crash of the database, all related in some way to long running PHP scripts with intensive activity on PG connections.
#1 - execution of an R call via pLR (sometimes this may crash it all by itself)
#2 - execution of a postGIS query (possible)
#3 - random occurences, all related to the same long running PHP scripts

I have read that perhaps hardware and/or system settings may cause this. I believe the system is running i9 processors, that may be set into some sort of virtual multi-threading mode. Thanks for any insight you all can give in tracking this down.

r.b.

Dump transcipt from postgresql log file:

LOG: server process (PID 5978) exited with exit code 2
LOG: terminating any other active server processes
WARNING: terminating connection because of crash of another server process
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.
HINT: In a moment you should be able to reconnect to the database and repeat your command.
<snip>message repeats 14 times </snip>
LOG: all server processes terminated; reinitializing
LOG: database system was interrupted; last known up at 2011-09-23 14:15:04 EDT
LOG: database system was not properly shut down; automatic recovery in progress
LOG: redo starts at 4AD/CFE63B98
LOG: record with zero length at 4AD/D0063FD8
LOG: redo done at 4AD/D0063FA8
LOG: last completed transaction was at log time 2011-09-23 14:19:45.972521-04
LOG: autovacuum launcher started
LOG: database system is ready to accept connections