I am in the same position, and there is a way to recover the sd to the default format, which is fat 32. Your problem might be that you've try to use it as MBR (Master Boot) and when it is formated to in MBR its really dificult to recover to default statement. what you can do is look for San Disk SD Formater, to chage its MBR format to Fat 32, instead of ready to stupid fighting to see who'se got a better answer! LOL
sincerely I hope you get to fix it, because it can be repaird with a software!