Hi all, we got ourselves 3 x Go professional 620. 2 of which we have set up without problem. the 3rd seems to be stuck with a 'wheel of death' on screen. We have done the reset on the unit and it does the drum roll and seemingly restarts. There is a very quick message saying that we need a map and then the wheel starts spinning and can't seem to get anywhere else. Is there a procedure i'm missing here?