Once in a while when I get stuck with something so oblivious that takes a hercules stress, but tends to have a simple solution I turn to Terminal. And I’d my USB stuck with write protect – somehow in rushing from one machine to other you don’t allays eject the USB drive properly so it gives you the hellish treatment, I tried formatting using Windows but it still won’t write on Mac though will read. In the end I slider towards Mac and used the following utility (found it on MacOSXHints). A much better and simpler solution than downloading any tool or any malware unnecessary.
>> diskutil eraseDisk HFS+ newdisklabel /mount/directory/n/disknamenum