This might be in the wrong area, but I will give it a shot- I have a Cannon Rebel T1i, and with it I have a Sony SDHC 4BG card. It has been used in my MacBook Pro before, and I was able to transfer the photos. But... It doesn't work anymore. I have had some issues with my computer reading hard drives in the past, but that was because they weren't formatted correctly. Nothing has happened out of the norm, and the card isn't locked. Any clues?