Welcome to Android Central! SD cards can become corrupted, or they might just be simply defective. What brand is it? Did you get it from a reputable retailer, or a random seller on eBay? How old is it? Lesser brands and older cards are more susceptible to failure or file corruption, while cards purchased from questionable online sellers are more likely to be counterfeit.
Unmount the card (in
Settings>Storage), remove it, and insert it into your computer. Then run chkdsk to look for bad sectors:
http://forums.androidcentral.com/amb...d-sd-card.html