help! 32G Extreme Card problem

Help! I was just shooting video on a 32GB Extreme Card on a  5D Mark II that I just purchased used from B&H.  While I was shooting I could use the playback feature and saw my footage just fine,  but when I got home and put the card in my reader – the card will mount, but it says there’s nothing on it.  I put the card back in the camera, and now its saying ‘no image’ …and when I put the camera in video mode to record is says ‘cannot create folder.’  The card is about 4 years old and I’ve never had any problems with it, and this is the first time ive shot with this used 5D.  When I put another card in the 5D and shot about 15 seconds of video my computer was able to read it and everything was fine.  Can anyone help? Is this a camera or card problem? and is there any way to recover my footage? Please help!