I have a 17 inch macbook (mid 2009) pro 2.8 GHZ which I just upgraded from Mavericks to Yosemite 10.10.5. I have my iPhoto file on an external hard drive (file is 318 GB) and it use to open fine in Mavericks. Now it won't open. When double clicking on the icon I get a window saying Preparing Library with a grey bar under it. The bar fills to about 17% and then seem stop and go no farther and the Photos program does not open. Any solution to this problem?