Image files won't open

I’ll extract files from a drive, I know the files are there… they even sometimes show up during the first Autopsy session. However when I re-open Autopsy, the same images aren’t there any longer and the external viewer will not display anything.

Sometimes even during the first Autopsy session, most image files will be viewable, however not all of them are. The files are easily viewable on the hard drive itself. Any suggestions/ideas?