DB fails to start: "Could not read from file "pg_clog/0003" at offset 212992: No error.

Hi,

We are using PostgreSQL 8.3 on Windows Server.

The db crashed and now it fails to start up.

The error is:

FATAL:  could not access status of transaction 4020264

DETAIL:  Could not read from file "pg_clog/0003" at offset 212992: No error.

Additional log from event viewer:

LOG:  database system was interrupted; last known up at 2012-07-12 11:35:00 CEST

How can we recover from the current state?

Thanks,

Olga