Photo Stream Thumbnail Missing

iPhoto '11 (9.2.3)

Recentely retrieved iPhoto library from Time Machine backup and found issues with photo stream pictrues.

Photo Stream Mar 2012, Feb 2012, etc. thumbnails are missing in events. When you click/select the even it opens to a list of empty thumbnails. When you select the empty thumbnail it opens and shows the picture.

In some cases in "photos" it shows an entire list of the same randam image. Again, when you select the photo it shows the correct photo.

How can this be fixed??

Many thanks in advance.