Hmm. It could be a fake card. What make and type is it. The other thing is somehow it got corrupt. A PC may be able to repair the file system or if you really have to will reformat it. I think the first thing I would do is talk nicely to someone with a PC. When connected, right click on whatever drive it appears on, properties, tools error checking and see if it can be repaired. If the PC won't read it it's probably counterfeit.