memory maybe distributed between different categories that you may not of, not only user files. first of all check the memory distribution by checking the : menu > tools > memory manager > options > memory details.
if you have alot of messages stored on the phone memory , try to delete some, especially the ones that have attachments or you have recieved through bluetooth.
if you have applications or themes installed on the phone memory , remove these and reinstall on the memory card.
Fear not those who argue but those who dodge