iPhoto does not want to edit certain pictures
Hi there
I am on iMac 5k late 2015 running OSX El Captain und have used iPhoto many times to edit pictures.
I recently went back in my photo library to 2011 and found pictures that have been imported from Nikon D200
that iPhoto does not want to edit anymore. When I click the edit button the edit mode opens but the buttons flash up white and then turn grey and do not respond. While recent imported pictures do edit properly I do not understand what happened and how to correct this.
If anyone can help me I would be grateful.
iMac with Retina 5K display, OS X El Capitan (10.11.6)