Corrupted Data?

Hello, pg_dump started failing for one of my databases, so I looked in
to it and it appears that I have some corrupted data or something.  I
assume this is related to a failed hard disk that was part of the linux
software raid mirror.

I backed up the entire data directory, and did a pg_resetxlog, but that
didn't help.  I found the specific row that seems to be the problem, but
I can't delete it.

Anyway, I don't know how to fix this, so if you could please help, I
would appreciate it.

Details are as follows:

[dbmail2@dezeut dbmail2]$ psql
Welcome to psql 7.4.2, the PostgreSQL interactive terminal.
dbmail2=# SELECT version();
                                                 version
---------------------------------------------------------------------------------------------------------
 PostgreSQL 7.4.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.2
20030222 (Red Hat Linux 3.2.2-5)

dbmail2=# SELECT oid,messageblk_idnr, physmessage_id, blocksize from
messageblks where messageblk_idnr =7718;
   oid   | messageblk_idnr | physmessage_id | blocksize
---------+-----------------+----------------+-----------
 2916427 |            7718 |           3842 |    524288
(1 row)

dbmail2=# SELECT oid,messageblk_idnr, physmessage_id, blocksize,
messageblk from messageblks where messageblk_idnr =7718;
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: Failed.
!> \q
[dbmail2@dezeut dbmail2]$ psql
Welcome to psql 7.4.2, the PostgreSQL interactive terminal.
dbmail2=# delete from messageblks where oid = 2916427;
ERROR:  could not access status of transaction 3822646358
DETAIL:  could not open file "/var/lib/pgsql/data/pg_clog/0E3D": No such
file or directory