This is not my GPS I have a 396 but it sounds like the same problem I had. If the clock setting is lost. (Dead battery) it looses its position and never figures out where you are.
In setup mode look for an option to set the time or bypass the quick start procedure.
If you get all your satellites this is not the problem but it sure sounds like the problem I was having.
I ran into something that made me think the problem was realted and sure enough the GPS is just fine now. Good thing to know before departing!
