Clog/Transaction problems

Hello,

I have a really weird problem; queries against a very large table are
failing against a very large table with a strange error. Case in point:

dqfull=# vacuum freeze mytable;

ERROR: could not access status of transaction 538989714

DETAIL: could not open file "/srv/db/postgresql/pg_clog/0202": No such
file or directory

WTF? The only activity this table has seen is a massive data import of
around ~40M rows. Is there a way to fix clog info and make it think all
transactions on it have committed? (Note: I tried a VACUUM FREEZE after
other commands were failing) What's a good strategy to fix this table.
I'd prefer to not have to reload it since that will take over 1 day.

Logan Bowers