OK my Nav system gets lost on some days, then is exactly, perfectly right other days. One day this week I received 0-1 satellites while on a stretch of highway, today got 5-6-7 on the same road. <p>Already had the receiver replaced in the rear-roof, what next? The box under the drivers seat? Is it just the DVD player (which seems to be working fine) or is there a CPU in there?<p>Thanks...