Thread: connection failure

I got a connection failure. The error message is like this:

Connection to database 'www2' failed.
pqReadData() -- backend closed the channel unexpectedly.
        This probably means the backend terminated abnormally
        before or while processing the request.

There are lots of pg_sorttemp***.* files. How can I connect to the
database? (The postmaster seems all right)
Aimin Pan