Postgresql 8.1.4 on FreeBSD6.1 core dump when pg_dump

[Julian Tree <julian(dot)tree(at)gmail(dot)com>]

Brand new system. Just imported the  database. Getting core dump when  
doing the following

- select on certain table,
-pg_dump.
- VACUUM ANALYZE VERBOSE (byt vacumm is fine)
- database is unstable, when connecting from php, it will  
unexpectedly quite..

Following is the error log, any insight appricated, I would at least  
like to pg_dump my data out of that trap.  Would also greatly  
appricate if someone can tellme what's wrong? Should I not use  
postgresql 8.1.4, or should I not use it on FreeBSD?

Aug 30 17:55:53 brian upsd[555]: frequency: 60.00, maxvac: 118.0,  
minvac: 117.3, voltage: 118.0
Aug 30 17:55:53 brian upsd[555]: load: 54.6, recharge: 100.0, temp:  
0.0, vdc: 13.69, output voltage: 118.0
Aug 30 17:56:05 brian kernel: pid 1632 (postgres), uid 70: exited on  
signal 11 (core dumped)
Aug 30 17:56:05 brian postgres[1634]: [7-1] FATAL:  the database  
system is starting up