Hi Lauren, and welcome to the Q&A Board!
So many others have had similar xD memory card problems. Several have had success getting the card back in working order, others have not.
I'm going to give you links to where these issues have been discussed and hopefully you can find something helpful. If not, please contact your camera or card manufacturer for help.
Even if you eventually can format the card, you may be able to get back many of your photos. Hope something here helps:
http://www.digicamhelp.com/cgi-bin/yabb/YaBB.cgi?board=access;action=display;num=1113273374http://www.digicamhelp.com/cgi-bin/yabb/YaBB.cgi?board=access;action=display;num=1096138468