You've probably already trashed the card, but if not:
The plastic toggle is there to activate a switch in the device (like in digital camera) not on the card. To get the device to see the card as unlocked, just glue a small piece of plastic to fill the slot in the side of the SD card casing. You will loose the SD card lock feature but at least you will be able to write data to the card again
Also, if you don't feel like gluing just stick a piece of tape on the side that will work too