I also have an Olympus SZ-31. Here's what's happening:
When I shoot videos and then take the SD card out of the camera and put it in my Mac, (videos are .MOV files) I can't get it to play. A message comes up on the computer saying Quick Time can't play the file and it may be damaged. JPEG pics come up fine. The videos play fine in the camera and also fine when I connect an HDMI cable to the camera and play them on a TV.
I have tried this on 2 different Macs - both have Mavericks - so it's not the computer. I have also tried 2 different SD cards and got the same result. I even tried reformatting the SD card and no change.
I can get the videos to play with Quick View or iMovie but in both cases the audio is missing.
I also checked the Olympus website to see if there was a firmware update and there isn't.
All of my other cameras, Canon, etc, work fine. I take out the SD card and put it in the computer, click on the video file I want to view and no problem. Quick Time opens the files and they play flawlessly.
I then tried an app I have called Smart Converter and it fixed the problem, but if I have to go through some kind of conversion process every time, that's ridiculous, plus you may lose image or audio quality in the conversion process. If I'm with a friend and want to give them the video, that doesn't work either. I should be able to just pop the SD card out of the camera, stick it in their Mac or even PC, load the file onto their computer and they have the video.
What's the problem? Thanks!