A useful link if you have SD card troubles

bruto

The SD Card association has, on its web page, a formatting program which is claimed to be the correct one for any card, and might speed up older ones that have become sluggish. I tried it on a 32 gig. card that started misbehaving in the camera, and later could not be read or formatted in my computer or camera. It seems to have recovered. If you're having problems with a balky SD card this site might be worth a look:

https://www.sdcard.org/downloads/formatter_4/