Apple released an update to iPhoto 5 today (version 5.0.1), which solves some issues that some users were having (me included). According to the release notes, the update:
... addresses issues with upgrading iPhoto 4 libraries, dragging albums into folders, importing MPEG 4 movies, and also includes a number of other minor fixes.The update is available via the Software Update menu, in most cases. In some cases, though, it's not recognizing that the new update is available. None of my computers showed the update as being available. To fix this, navigate to the Receipts folder, located at /Library/Recipts. Next, find all of the iPhoto files located in that folder. I had four files related to iPhoto (iPhoto.pkg, iPhotoContent.pkg, iPhotoUpdate401.pkg, iPhotoUpdate403.pkg). To make the 5.0.1 update work, drag those files out of the Receipts folder and put them some place safe (the Desktop is fine).
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050202182547731