Users cannot Edit just their own Scoops

I've noticed on my Drigg site that non-admin users cannot edit just the Scoops they've submitted.

User access permissions for "Edit Own Drigg Stories", and for "Edit Own Promoted Drigg Stories", have been enabled for these authenticated user classes. But they cannot edit them.

Note that I haven't given them permission to "Edit Drigg Stories". This is because when I do, they are suddenly able to edit Scoops submitted by other users as well. This of course is not optimal. We don't want any authenticated user to be able to edit just any Scoop - just their own.

Is there something I'm missing? My site is here, by the way.