Share your experience!
If you have the money,go for class 10.That is what I have on my Z1.
I think the microSD might have corrupted them. Does the same happen with internal memory?
If you save videos to internal memory,they work fine,right?
Try settings-apps-all-camera,force stop and clear data.Restart.If this does not help,perform a software repair.
Can you try the software repair? It is a little different.