If it don't work in 2 devices and can't be formated by your computer, it means that it's defective.
You can try formating it with another computer, just to be shure.
Your card have a waranty covering that kind of deffect. The waranty don't cover any loss of data, but state that it covers replacement of a defective or faulty card.
Return it to the store where you bought it to get a replacement.
Electro, October 2013