cache lookup failed for relation X

I found some posts be developers discussing this issue last Jan. and Nov..
See link below.

http://search.postgresql.org/search?m=1&q=cache+lookup+failed+for+relation
&l=&d=&s=

But have not been able to find any suggestion on how an end user can use
to get around this problem. Basically, we have a table X, trying to drop
it would result an error message below:

cache lookup failed for relation XXXXX

I am using PgAdmin and I can still view the schema of this table, but
any operation on it would get the above error.

Any suggestion on how to drop a table in this situation.

I am also wondering whether this problem has been fixed in newer
PostgreSQL releases.

BTW, our postgreSQL version is 7.4.3.

Thanks.

____
This communication may contain information that is confidential, privileged or subject to copyright. If you are not the intended recipient, please advise by return e-mail and delete the message and any attachments immediately without reading, copying or forwarding to others.