I just upgraded my Lumia 1320 to Windows 10 this morning and right after finnishing the installation, Start Screen showed up, but after trying to make a call, when I want to switch back to start screen it says ''Loading'' for a few minutes and then just switches back to the last app used or locks screen if it times out, but it won't load the Start Screen. Is the a solution to this issue? Has anyone experienced it? I can't even use my phone now! Thanks guys...