Got the same problem here after moving to a new server.
I noticed that images that were mass uploaded are gone.
The images that are still working start with the userid, the ones that are gone don't.
gallery/files/1-meeting-trs-038_575036.jpg < - Working
gallery/files/Suzuki-intruder-1400018.jpg < - Broken
Strange thing is, that the images that are mass uploaded are also gone from the server but were working before i moved.