read this articles , may help you to fix your flash drive
http://www.flashdrive-repair.com/2013/11/8-ways-to-fix-write-protected-usb-flash-drive-and-memory-card.html
and
http://www.flashdrive-repair.com/2012/12/how-to-repair-usb-flash-drive-in-three.html
Ashraf Mansour
December 2013