[aiharkness]

The backup with desktop manager does not backup the media card. Perhaps they meant the media sync (using Desktop Manager ver. 6) will copy the files to the computer, but I don't see how if the card can't be read, and then only if Desktop Manger is configured to automatically sync media.

I don't know mac computers, have never used one. But isn't there a stock disk utility that will scan the card for lost sectors and file system and media errors?

At any rate, zerog46 is probably right that the card is DOA. Only way to know is to try and repair and recover your files, or short of that, reformat the card and see what happens. If you give up on trying to recover your files, you may be able to reformat the card using the handset. But me, I would recover my files if possible, then get a new card.