My 5100 can't play back video. When I press "Ok" to play video in playback mode, I get the timer on the black screen for a second or two, then goes back to the video "thumbnail". Sometimes it makes a shutter sound, sometimes it does not. But no matter what, it does not play the video.
The video *is* recording, however, because when I connect my SD card to the computer I can play it back just fine.
I did a hard reset and that didn't help. Any ideas?