The AR5BX63 card uses the Atheros AR5007EG chipset. Madwifi currently has a ticket open for adding support for this chipset. http://madwifi.org/ticket/1192
Information about this chipset can be found on this Atheros website. http://www.atheros.com/pt/AR5007EG.htm
Windows 2000/XP Drivers: http://www.empiatech.com.tw/support/IC_drivers/PCCAM_WHQL_Standard_Installshield_072007.zip