Error message: 'ERROR: cannot mark block 0 of [] blind'

Hi all,

Does anyone know what this error means or whether I should be concerned
about it?

'ERROR: cannot mark block 0 of [] blind'

It occurred while performing a simple query through the ODBC driver.
The query was:
SELECT keyword FROM modkeyword WHERE mfrname='DEDE' AND model='VM7451'

The definition of modkeyword is:
Table "modkeyword"
Attribute | Type | Modifier
-----------+-------------+----------
mfrname | varchar(8) |
model | varchar(25) |
keyword | text |
Index: modkeyword_pkey

There are about 3000 records in this table.

I checked the table through psql - nothing seemed amiss, but the error
was reproducible on a different workstation. Restarting postgres on the
server did fix the problem and there don't seem to be any ill effects -
but could anyone comment on why it happened and what it means? And,
perhaps, a means of avoiding it in the future?

System information: PostgreSQL 7.02 on Linux i686 kernel 2.2.14.

Thanks!

Francis Solomon
IT Manager
Stellison Ltd.