I had to restore my iOS 5.1 iPhone from iCloud after recieving a replacement. Many of the thumbnails for photographs are now black. Is there a way to regenerate them?
Wait and see. When I looked the following morning, the black thumbnails had all been regenerated automatically.
I may have experienced something similar the other day when my new iPad (3) arrived, and I restored to it from my original iPad (1) backup. I happened to be in the Photos app (on the new iPad) when I initiated the syncing of my photos. When it completed, I noticed that all my albums were now there in the Photos app—that none had thumbnails.
Solution (worked for me): 1. quit Photos (tap-and-hold on any icon, wait for the "jiggles" and then tap on the red "x" for the Photos app). 2. re-launch the Photos app.