I had a SanDisk 64 that I was using for a few months recording stills & video just fine. Then a couple of weeks ago it would only record stills. I did a full reformat but still had the same problem. I contacted SanDisk and they said that was very unusual but they warranty them for life. You must have the purchase receipt which I did and I returned the defective micro and I should receive a new one tomorrow.
I also use two other identical micros that record just fine.