OK, I have a 256MB SD card that I want to use to backup/transfer a few documents from my Mac to 3 or 4 PC's. I'd really rather do this than send over the network left and right. The problem is that when I copy a file to the card, it becomes unusable. The format stays consistant, but if I run a file from the card, or even copy it to the card and then back to the desktop and try and run it, no dice. The card has recently been formatted, and seems to work fine in my PC when trying to perform the same actions. Help?