I know the solve, we have it daily here on our company. It is the FAT compatibility that hangs it. Try hundereds of cardreaders, best work with PocketPC devices.
Do not try to undelete, "recover" it with some tool. Just try the most strange devices, like mp3 players, camera's etc. to read the card. If it reads, copy your data to safety, then reformat your card in that device and it will work in other devices again.
