>Harry,
>
>It's possible you don't have delete rights on the table or that foreign key constraints are preventing the rows from being deleted.

Yes, I thought of that, but I checked permissions and I appear to have them all. I don't know if this will give anyone a clue, but I logged in to the database using "Enterprise Manager" and - initially - failed to delete even from there. Until I did it in small chunks. It would allow me to delete about 5000 rows without protest. Above that I got "unknown error".