I actually had this happen to me twice last night with an Ultra II 4GB and an Extreme III 4GB out of two seperate cameras. I thought I had a card problem when the first one did it. Recovery software couldn't read it so I checked in the camera again and the first file was corrupt so I deleted it in camera. After that I was able to read the card in Explorer but not in LR so I was safe anyway. 1hr later when downloading the card from the other camera the same thing happened. "Your card is not formatted, do you want to format it now?"
I thought that this was too much of a coincedence so swapped to another reader and 'No problem'
I just hope that your's is the same.
