iPhoto 6: White lines in thumbnails

When viewing thumbnails (small images) in the iPhoto Library, you may see white lines through an image that do not appear when viewing the image at full size. These steps should resolve the issue:

1. Quit iPhoto.
2. Update to iPhoto 6.0.1.
3. While holding the Command and Option keys on the keyboard, open iPhoto.
4. When prompted, select the option to "Rebuild all of the photos' thumbnails."
5. Click Rebuild.