pg_clog problem (PG version 7.4.5)

hackers,

I am having a problem with table (identified by pg_dump).  I get the follow error when I try to COPY the table to 
stdout (or /dev/null).

DB=# copy rnk to '/dev/null';
ERROR:  could not access status of transaction 1076101119
DETAIL:  could not open file "/usr/local/pgsql/data/pg_clog/0402": No such file or directory

Pg version is 
select version();                                            version
-------------------------------------------------------------------------------------------------PostgreSQL 7.4.5 on
i686-pc-linux-gnu,compiled by GCC gcc (GCC) 3.3.4 (Debian 1:3.3.4-6sarge1)
 

I do have a good backup from the day before, if needed.  is there a magic command to get me out of this?

Thanks
Jim