This happened to me a couple of days ago, good footage, card showed I had a 250mb+ file but wouldnt open in any format, Just a kalidescopic page.
I copied it across to my Mac, tried wondershare ultimate to change it to different formats, still no luck, didnt delete it from the card, did some more filming the next day, when reviewing the new footage, lo and behold the so call corrupted footage was actually there.
I put it down to 2 things, I did a hot swap of batteries, before turning off the video button on the app during the intial filming , and the second thing I think a reseat of the card in and out of the quad may also have helped.
Just a thought