HELP speed up my Postgres

Hi ALL,

Ive been using postgres for 3 years and now we are having problems with its
performance.

Here are some givens..

We have 260 subscription tables per Database.
We have 2 databases.

Our main client has given us 250,000 mobile numbers to deactivate.

--
We we are experiencing
91,000 mobile numbers to deactive it took a week to finish for 1 DB only
the second DB is still in the process of deactivating

Algorithm to deactivate:
we loaded all subscription tables names into a table
we loaded all mobile numbers to deactivate into a table

SQL:
update SUBSCRIPTIONTABLE set ACTIVEFLAG='Y' where mobile_num in (select
mobile_num from LOADED_MOBILE_NUMBERS)

the script was made is "C"

COFIG FILE:
# This is ARA nmimain

tcpip_socket = true
max_connections = 150
superuser_reserved_connections = 2

port = 5433
shared_buffers = 45600
sort_mem = 40000
max_locks_per_transaction=128

#fsync = true
#wal_sync_method = fsync

#
# Locale settings
#
# (initialized by initdb -- may be changed)
LC_MESSAGES = 'en_US.UTF-8'
LC_MONETARY = 'en_US.UTF-8'
LC_NUMERIC = 'en_US.UTF-8'
LC_TIME = 'en_US.UTF-8'

.. DB is being vaccumed every week
my box is running on a DUAL Xeon, 15K RPM with 2 G Mem.

that box is running 2 instances of PG DB.

TIA,