on 64Bit BT5, "xgps" (Applications -> BackTack-> Information Gathering -> Network Analysis -> WLAN Analysis) requires a 64bit swt.jar.

I downloaded the 64bit swt package from this location specifically this zip file, unzipped the package and copied the swt.jar file over to the /usr/share/xgpsmanager directory (replacing the old 32bit swt.jar file.)