Error message, which memory param should I increase?

I have a very large query which needs to be very large, and it gives me this
error sometimes:
"Error","7175","06/23/03","23:52:52",,"ODBC Error Code = 08S01
(Communication link failure)<P> Error while executing the query; Out of
memory while reading tuples.

Previously I had done:
1) in /etc/sysctl.conf
kernel.shmall = 134217728
kernel.shmmax = 134217728

2) in postgresql.conf:
shared_buffers 10000

The machine has 2 processors, and 1gb of real memory, linux kernel
2.2.14-5.0smp Postgres 7.2.4, many gigabytes free disk space. Can anyone
tell me what I should do to further try to prevent this out of memory
situation?

Additional info, here is the memory segment of my postgresql.conf:
#
# Shared Memory Size
#
#shared_buffers = 64 # 2*max_connections, min 16
shared_buffers = 10000 # 2*max_connections, min 16
#max_fsm_relations = 100 # min 10, fsm is free space map
#max_fsm_pages = 10000 # min 1000, fsm is free space map
#max_locks_per_transaction = 64 # min 10
#wal_buffers = 8 # min 4

#
# Non-shared Memory Sizes
#
#sort_mem = 512 # min 32
#vacuum_mem = 8192 # min 1024

#
# Write-ahead log (WAL)
#
#wal_files = 0 # range 0-64
#wal_sync_method = fsync # the default varies across platforms:
# # fsync, fdatasync, open_sync, or open_datasync
#wal_debug = 0 # range 0-16
#commit_delay = 0 # range 0-100000
#commit_siblings = 5 # range 1-1000
#checkpoint_segments = 3 # in logfile segments (16MB each), min 1
#checkpoint_timeout = 300 # in seconds, range 30-3600
#fsync = true

Thanks

Terry Fielder
Manager Software Development and Deployment
Great Gulf Homes / Ashton Woods Homes
terry(at)greatgulfhomes(dot)com
Fax: (416) 441-9085