My fishing buddy has a 642c, he brought it over to my house since I have a 640c so the wiring is the same. When you power it up you should be able to hit Menu 2 times to get to routes etc, but on his it for some reason only lets you press it 1 time. If you hit it 2 times it exits. I hook mine back up and mine is fine. Any ideas, this was working properly up until about a week ago. Thanks.