unexpected shutdown

My database has shutdown several times in the last couple days. I have no
idea why. I am running centos and I have not rebooted the server or made
any configuration changes. I am running postgres 8.2 and it has been
stable since I installed it about 5 months ago. The databases crashes and
so my software application goes down. When I restart my application
everything seems to work fine. But then it crashes again, something
appears to be corrupt. Here are my logs:

LOG: server process (PID 501) was terminated by signal 9
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.
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.
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.
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.
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.
FATAL: the database system is in recovery mode
FATAL: the database system is in recovery mode
LOG: all server processes terminated; reinitializing
LOG: database system was interrupted at 2007-06-17 10:55:32 PDT
LOG: checkpoint record is at 0/72F41748
LOG: redo record is at 0/72F41748; undo record is at 0/0; shutdown FALSE
LOG: next transaction ID: 0/2638157; next OID: 52761
LOG: next MultiXactId: 4; next MultiXactOffset: 7
LOG: database system was not properly shut down; automatic recovery in
progress
LOG: record with zero length at 0/72F41790
LOG: redo is not required
LOG: database system is ready

LOG: server process (PID 13904) was terminated by signal 9
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.
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.
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.
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.
LOG: all server processes terminated; reinitializing
LOG: database system was interrupted at 2007-06-18 10:09:51 PDT
LOG: checkpoint record is at 0/73609D18
LOG: redo record is at 0/73609D18; undo record is at 0/0; shutdown FALSE
LOG: next transaction ID: 0/2645768; next OID: 52761
LOG: next MultiXactId: 4; next MultiXactOffset: 7
LOG: database system was not properly shut down; automatic recovery in
progress
LOG: record with zero length at 0/73609D60
LOG: redo is not required
LOG: database system is ready