Bob
I have this problem, randomly, sometimes more from the Ipod than the computer.
Usually it's my own photos though
and never all of them maybe 10%. quite often I get half a picture
I have found that the next time I view it changes so have been blaming download speeds.
It's a pain at times but I just live with it as it is random
what can you do.
I also run a mac , don't know if that's a factor
sandy