postgres 8.1 crashing

Hi!

I just upgraded pg 8.0.3 to 8.1 (dump and reload) and outcome was a
corrupted database. pg 8.1 seemed to fly but backends were crashing
:-/

Hardware is Sun v40z with 64bit Debian Sarge, Linux 2.6.13.2. Size of
database is somewhere around 500M rows and it's loaded by a website with a
lot of traffic.

Configuration:
   http://tuner.bdb.fi/postgresql.conf

Some backtraces (update queries are included in the bt):
   http://tuner.bdb.fi/pg_crashing.txt
   http://tuner.bdb.fi/pg_crashing2.txt
   http://tuner.bdb.fi/pg_crashing3.txt

And users-table which is involved in all the crashes is described
here (contains ~700000 rows):
   http://tuner.bdb.fi/pg_crashing_table.txt

I tried to reindex the table but it didn't help. PG went corrupted
after a while:
   http://tuner.bdb.fi/pg_crashing4.txt

Any ideas?

     |\__/|
     ( oo )    Kari Lavikka - tuner@bdb.fi - (050) 380 3808
__ooO(  )Ooo_______ _____ ___ _ _  _   _    _      _                  _
       ""