Ditto on the symptoms in my Samsung Galaxy Note II. My 64GB SDXC sarted doing the same things after nine months of perfect service: videos won’t delete, pictures from my camera corrupt and it won’t format.
The OS on my phone hasn’t updated in quite some time and nothing else weird occured. I submitted a request for a warranty replacement since I’ve only owned it for almost ten months. I don’t really expect a resolution but wanted to post my experience here too.