Horr Grasshopper,
On my second 660 and love it. The first one gave me hell though.
You can try the. GPS Simulator button for indoors use may be ON
Go into the MENU Screen and select :
TOOLS
SETTINGS
SYSTEM
GPS SIMULATOR – in here, the simulator should be OFF. for normal use
this function is used if you want to use the unit indoors away from satellites and simulate your trip
hope this is the fix you are after.