I had a bad reader sent with my Expedition C, and Lowrance was quick to send a new one when I called, but I had also found out a workaround that will let you use any card reader with MapCreate (I've never used the Lowrance reader and have had no problems).
Put the memory card into the GPS unit, start it up and go to the following menu to register a card as usable to MapCreate:
Menu -> Menu -> Browse MMC Files -> MMC Card Info (button at bottom of screen) -> Create ID File
Then you should be able to use that in any card reader on your computer with MapCreate, it will ask you to register it as one of your five allowable cards and you're good to go. This came from Lowrance and they said it will work with any color unit, and it's worked with two cards with mine. Good luck.