Recovering data from corrupted table. Urgent Help!!

Hi:

Is there any way to recover data from a corrupted table? I can only run
SELECTs on certain WHERE conditions.

I cannot vacuum, pg_dump, I've deleted the indexes and try to reindex,
always get error:

ERROR:  could not access status of transaction 4244329
DETAIL:  could not open file "/usr/local/pgsql/data/pg_clog/0004": No
existe el fichero o el directorio

Thanks a lot.