I have been trying to get my iPaq 3870 to sync over WiFi for ages. Fine in
the USB cradle, but will only connect as guest by WiFi. BUT when I
disconnected my DSL internet connection, ActiveSync made the WiFi connection
fine, and also initiated an internet dial up.
i.e. disconnect your internet connection, and you may get a work around for
802.11 syncing / back up. The internet connection can be re-made once the
device has connected.