Dealing With Misrotated Photos
When copying photos to another iPhoto library, sometimes some of the copied photos will have a different rotation in the destination library than they did in the source library. The most common problem is that sometimes, after performing a copy, iPhoto generates a thumbnail based on the original version of the photo, but fails to update its thumbnail once the rotated version of the photo is copied to the library. If this is the case for your library, then if you double click the photo to view the full sized version, the properly rotated version of the photo will be displayed. To fix this problem, all you need to do is to rebuild the thumbnails of your library. Instructions for doing so can be found on Apple's site, iPhoto 4 or later: Rebuilding the iPhoto Library.