small number of photos and videos won't load and show a timer moving in bottom right corner

HI. I have some photos and videos in my albums which, when selected:

- don't become clear if they are photos, they just show a small analog-clock-like blank face in the bottom right corner, with a white arm moving around and filling the face. Even when it is full, nothing happens.

- don't play if they're videos, and have the same clock thing as above.

Anyone encountered this and know how I can retrieve my precious videos and pics?

4S, not yet upgraded to IOS9

Thanks!