The FB3 will support most sizes of XD card, up to a few GB. The main thing is that CURRENTLY, the FB3 only supports "Standard" (sometimes denoted with the letter S) XD cards.
Recently XD cards have been release with other letter designations, such as H or M. These letter designations will currently NOT work with the FB3. We will release a different version of firmware one day that will support the H and M cards. In the mean time, you will need to use XD cards that either have no letter at all, or have the letter S.
Best regards,
William Benner