PANIC: unexpected hash relation size

Hi,

I'm using Postgres 8.2.2 on Windows.

I frequently get this error message:
PANIC: unexpected hash relation size: X, should be Y

There is no specific point where I get this error, it can occur anytime
after a SELECT/INSERT/UPDATE. I've never got it after DELETE so far.
When it occurs, the server needs to be restarted (otherwise pgAdmin
disconnects after each access attempt to any DB object). After restart,
any query I run on the same table I was querying before (sometimes also
on other tables), results the same error with different values (X,Y).
Only way I could get rid of this error was dump the database, drop it,
then restore it. After a few minutes/hours/days the error occured again
however.

My tables are small (few thousand records max), I rarely use indexes.

I searched the Google for the error message, but found nothing, only
some source code of Postgres.

Has anyone ever recieved this error?
What could be the cause?
Is it a bug, or I'm doing something wrong?

Thanks in advance,
Csaba