I have had my MBPr for about a week now and have opened up iPhoto quite a number of times but today, on launch, it said it 'needed to generate high resolution thumbnails' . This took a few minutes as I don't have a lot of pics in iPhoto.
Any idea as to why this only happened today and not on the first launch of iPhoto?
Thanks in advance
MacBook Pro with Retina display, OS X Mountain Lion (10.8.1)