Won't return to home screen

I have a iphone 3gs that will not return to home page unless I turn phone off and on, then once I select an action I can't get it return when I press home.

I don't believe it the home button because I got this motherboard online with this stated problem, so I believe it has something to do with the motherboard?

Everything else works just fine, except I get a No Service, But when I going to settings and select About it shows the phone number of the SIM card, moved SIM card to a known good phone at same location and I get service, Again if I turn the phone off it will show the home page when I turn it on again.