When a subscriber attempts to modify an image, the page displays the text -1 instead of the modification tools.
- Log in as a Subscriber.
- Navigate to a media gallery and click on an image uploaded by the subscriber to open it.
- Click Edit, and then click Modify on the page that opens.
Change default WordPress user role from Subscriber to Contributor. You may also need to change roles of previously registered users.
Check the related discussion at http://community.rtcamp.com/t/subscribers-cant-modify-images-they-get-weird-1-displayed-instead-of-tools/1045/2.