pgAdmin II error

I was trying to updating a row in a table that I created using pgAdmin II
(version 1.3.60, postgresql version 7.2.1).

Here is what I did:
1. open SQL Output window
2. click on a row
3. click on EDIT button
4. update the data in a column
5. click on SAVE

I got error "could not locate the record for updating in the database".
Anybody has seen this?

Thanks.

YR