I'm not sure if this is the right place to ask this question - but here goes.
When I purchased my D5100 in November last year, I also purchased a Lexar Platinum 11 16Gb memory card.
I've had no problems with it until 2 days ago. I'd taken some photos and was transferring them to my pc via a USB cable. Two of the photos appeared to have been 'cut in half' i.e. part of the photo appeared but the rest of the image was blank. When I looked at the individual images on the camera the problem photos appeared to be ok. But I did find one video that had a red cross showing instead of a thumbnail. If I click on the red cross I see a message that says 'cannot display this file'. If I try to delete the file I get a message saying "The memory card cannot be used. Card may be damaged. Insert another card"
I took more photos yesterday and when I transferred them to the pc 2 of them were only partly processed - again they looked as if they had been cut off while they were being processed.
I'll talk to the people at the shop where I purchased the camera and memory card - they aren't camera specialist so they probably won't be able to help with any technical support.
I want to keep taking photos but I don't want to risk using a dodgy memory card.
The Lexar website indicates that the Platinum 11 memory cards have a lifetime warranty but Lexar doesn't have an office in New Zealand.