I think i've found a Bug. In editing Overlay ads when editing.
If you change the settings of one Overlay Ad it gives an error Message Like:" Not edited" or something. Additionaly the edited Ad is the same as the other Overlay. Means: The edited Ad has exactly the same specification of another existing Ad.
Steps to reproduce:
Create TWO different Overlay Ads.
Edit ONE of the Ads.
You will see the Error Message and after that you will have two Overlay Ads with the same Specifications.
EDIT: Found the Bug. In overlayedit.php the sql query is missing a WHERE