Hello again - the 'fix' lasted about a week (I do a good deal of photo editing and am just back from DC with another boat load of Cherry Blossom pics) and now am back to getting about 6 crops in before the system freezes. It only freezes in 'Crop' or 'Straighten', if I don't use those, I can edit all day. I redid your suggested fix from previous emails with no positive impact. The main hard drive on my iMac is pretty full, so I do all my iPhoto work on an external hard drive and then have another external hard drive for backup. I am thinking of doing a clean Yosemite install and then going back to doing all my iPhoto work on the main drive and then backing up. If I do the clean install, will that likely take care of whatever glitch is currently preventing successful iPhoto editing? I have also thought of using my Adobe Elements 13 (which I now only use for pano-photo merging) to do my editing, but that is a more ponderous process and I would rather not as I don't need to or desire to do a more intense kind of editing. I never had a problem with iPhoto in the previous operating system and would have gladly stayed with it were it not for the fact that some software updates and some hardware (my new Apple router) require Yosemite. Any help or suggestions is much appreciated. tb