Took my X to a corp store recently because when connected to my PC via the USB cable, I got "Memory card is missing". The VZW tech worked on it and when I got home, I still got the same message. I emailed the tech and she said call *611 and they will send you a new card as I have made a notation in your account.
Got the new memory card yesterday. Followed the instructions on the card package(includes a card reader btw) and...I still get the same message.
Taking my X and the new card back to the corp. store soon.