Card is dead! I put it in my PC and it is unrecognized. I checked my old 8gb Samsung card from my Contiuum in the adapter and it popped right up.
So that's it. No warning, no signs of decaying performance it literally died while my phone charged overnight.
It is a major problem that a card should die after light to average use in less than six months. Hopefully they can fix this in a future update.