If photos are nested (in a folder within another folder) in folders or albums, you may see a "communication error" or other odd behavior when you try to display them with Front Row.
To successfully view photos with Front Row, make sure that your images are contained within an album available in the iPhoto Source window. You can't view images within folders or albums that are inside of other folders or albums—those that aren't available in the Source window—unless you expand the folders in the Source window so the nested folders are visible.