My Navman F20 does not recognize any zip codes or addresses in the Eastern USA time zones, which is where I travel
It does fine here in Illinois, but when I try to input any address outside East of here it fails to recognize it. I notice that upon turning on it downloads certain maps, none of which are in the East area, but neither is Illinois.
GPS - Navman - F20 GPS Receiver
Answers & Comments
My father had a similar problem with his Navman here in the UK. I discovered he had turned off sections of his mapping software in the Navman - take a look at Preferences -> Maps -> Manage Maps to see if any areas are turned off.