Need help ! --backend closed the channel unexpectedly

Sorry for my bad English also I am newbie in Postgres.

I have running PostgreSQL 7.0.2 on RedHat 6.0 for 2 months without problem. Just today when I
tried to connect, I recevied following error messages:
======================
[poo(at)data poo]$ psql pioneer
psql: pqReadData() -- backend closed the channel unexpectedly.
This probably means the backend terminated abnormally
before or while processing the request.

======================

Now I cannot connect to the database any more. Even I stop the postmaster process and then
restart, but received the same messages .

Can anyone help me how to solve this ?

Thanks in advance.
Poowasun

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