I am using an older macbook pro with lion 10.7 OS with iphoto 11 and aperture 3. My iphoto library is a rebuilt one because I did have trouble with the original. All has been working fine. Suddenly I cannot edit. On certain photos I get a message saying cannot edit because the photo was processed on an older version photo software. Not true. Picture was loaded and edited in Dec. 2012 and I have not changed anything with photo apps. On some photos if I click on them the program freezes. I think something needs to be "cleaned up but not sure where to begin. I checked my disk utility and that is fine.
Typically this is because a photos was edited with an old version of iPhoto - I forget the cut off but maybe iPhoto 6 or earlier - to edit with the new versipons of iPhoto '11 you have to duplicate the photo prior to editing