I had exactly the same thing happen to me using Extreme III 4Gb after 2 years use. You can’t format/recover a card when your computer and camera tells you the card doesn’t exist! I tried the card in a number of other camera and readers and all say ‘no memory card present’.
On the other hand I have another camera with a standard ealry 256MB. THis card has had a lot of use over about 10 years and is still going. I am now wondering if the Extreme cards are more likely to fail.
