Contact DoubleDip (A member on here) from Ultimate Wiring Conversions.
He programmed my system up and enabled the rear speakers (Mine was from a Maloo Ute, so the rear fader was disabled), enabled the DVD input, disabled the Video in Motion Lockout, enabled the rear view camera, and did a software update.
With the Nav system, just check the Nav antenna connection (The blue Fakra connector on the passenger side of the unit).
It may be loose, or the antenna cable may be kinked or damaged.
(I think there is a GPS Signal strength screen on the Nav Configuration section, which will show GPS signal strength).
Hope this helps.