#1. "RE: D5100 and Lexar Platinum 11 SDHC memory card" In response to In response to 0
Sorry to hear of your problem.
Sounds like the memory card is corrupted.
If you don't already have one, I would recommend getting a Memory Card Reader and use it to download your images to the computer. I always use a card reader to download the image files from the cards to the computer.
If that doesn't work: Before you delete the files or format the card you can use Image Recovery software to recover the corrupted files. Both Sandisk and Lexar have Image Recovery software available on their websites. You can purchase it though their site or buy one of their high end cards that include an activation code for the recovery software making it free.
After recovering the images you should format the card using your computer via a card reader. Then format the card in the camera before you capture another image. If the problem persists, get a new card. Remember to format the new card in your camera before using it. Then always format the card in your camera after you have downloaded all of the images to your computer.