Which Ambicom card do you have? There is the older BT2000E, which is supported, and the newer BT2000C which is not currently supported. To see which model you have if there are no physical markings, type 'cardctl ident' in the terminal app with the card in your Zaurus.
If you are using the stock Sharp ROM and have the BT2000E, you only need to install
bluez-zaurus_2.3-2.4.18d_arm.ipk and delete the file /etc/pcmcia/bm3.conf