Personal Hotspot on my iPhone stopped working after iOS 6 upgrade. My Mac connects to it over WiFi, but the icon of WiFi is with '!' and the System Pref > Network says either 'you have self assigned ip' or 'you don't have ip' and of course there is no internet to my Mac. This feature works just fine on iOS5 and I haven't changed anything in settings. Actually the Personal Hotspot works even now if I connect WITH CABLE, but not over WiFi. And of course the internet works fine on iPhone itself.