I got my card before I got the phone, but was having problems with it. It would fail to format on most attempts(no matter what device I was using to format it), I would get a message on my phone that the card was damaged, and it would have trouble mounting. I sent it back to the seller and they confirmed it was defective. Then I got an interesting email from the seller stating something like this: your replacement order has been delayed. Sandisk has been experiencing a higher than normal return rate on their 64gb cards and has recalled a part of their inventory. They will be replacing the defective units with working ones. Expect a delay of about a week. So anyone experiencing problems may want to contact their seller or Sandisk directly to see if you are part of the recall. I know others on xda were having similar problems but didn't know anything about the recall. Thought I would post here to pass along the info I received.