Transaction error

Hi,

I recently shut down my machine (as far as I know, it went down
cleanly).  When I brought it back up, one of my databases was messed
up.  Here is the error I get when I try to select:

ERROR:  could not access status of transaction 4114057
DETAIL:  could not open file "/var/lib/postgres/data/pg_clog/0003": No
such file or directory

I tried restoring a backup of the data directory that did contain the
0003 file, but that didn't work either.  I don't have a copy of the
dump before the crash--though I think that is what I'll backup next
time.  How can I get my data back?

Debian GNU/Linux
postgres 7.4.7

Casey