There are times when I try to ZOOM in on a map on the unit and it makes the unit shut off. Has anyone else seen this before? Sometimes I try to access the FIND function and it will do this too. It only does this when I have the GPS on batteries, not when its plugged into the 12v port in the truck. I have changed batteries and it helped for a while. The battery indicator tells me its at full strength. Is there something seriously wrong with my Vista?