iPhoto can see thumbnails but cannot get full pictures

My iPhoto library seems to be corrupted.

I can see all the thumbnails but when I click on some I get a triangular sign with an exclamation point.

Others work.

Thinking that perhaps the iPhoto database was corrupted, I attempted to load an older time machine backup (mid July 2014), but Time Machine would not let me select the iPhoto directory. I can select my desktop ( as a test) but not my documents (very upsetting).

I did successfully restore the iPhoto App.

I have successfully restored my complete system twice with only minor problems. One was a permissions issue when I restored to a new MBP.

Anyway in both cases the iPhoto library stayed intact.

I would deal love to hear any suggestions that anyone might have to offer.

Thanks

Barry