The application associated with the car dock (don't know what it's called), automatically opens when you put the phone in the dock right?
If you press the "home" button, does it go to the default home screen of the phone? Is it supposed to do that? When I first got the dock it didn't.
Then I installed the car home app from google, CarHomeLauncher.apk and com.android.vending-1.apk respectively. At first it installed with no warnings.
I got bored one day, so I un-installed car home in Application Manager... But I soon realized Car Home was better than the stock. So I tried to install it again. I first installed CarHomeLauncher.apk, went well. Then I installed com.android.vending-1.apk again, thinking I still need it, then the phone gave me a warning saying "You are trying to install over a system application, do you want to continue" or something to that effect. Now, even while using the stock application, I can press on the home button and go to the default Moto Screen in landscape.
Maybe the devs can see this as an entry to the system? Or maybe nothing.