Solution :
- connect device to your PC (USB connection) and make sure its set so that you can copy files to/from your computer (on my device in the notification panel theres an option to do this under USB connected)
- on your pc, open windows explorer (or click on start->computer), then right click on the mapped drive to your sd card you may have to wait a minute or two for the mapping to take effect
- select Properties
- select Tools
- select Check now (for error checking) to automatically fix file system errors (no need to deal with bad sectors at this time)
- when completed (takes a minute or so), the FAT will be in working order once again. No files are deleted during the process, so no need to worry about that.
- safely disconnect the device from your pc, at which point the sd card will now be mounted read-write and youre good to go
- Android Central