Unable to access records in table!

Hello guys,

I have a problem when launching a query on a table:

When I submit: SELECT COUNT(*) FROM billing;
the output is this:

FATAL 2: open of /pgdata/pg_clog/0353 failed: No such file or directory
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: NOTICE:
Message from PostgreSQL backend:
The Postmaster has informed me that some other backend
died abnormally and possibly corrupted shared memory.
I have rolled back the current transaction and am
going to terminate your database system connection and exit.
Please reconnect to the database system and repeat your query.
Failed.

Indeed /pgdata/pg_clog/0353 isn't there!
Yesterday the file had a different name... It seems that every day a mew
file is created...
Does anyone of you knows what this means?

Thanx!

Wim