It's an unfortunate truth that online people act in ways that they wouldn't in real life. If you pay attention to any game that you play competitively online you will notice that steps have been taken in order to prevent unscrupulous people from "griefing" those that just want to play as intended. It appears that something slipped through QA on Magic 2012. As I write this post I'm in the middle of a duel online. It's my opponent's main phase, he's at 6 life with 1 land and no other permanents in play. I'm at 10 life with Ulamog a ton of land and another creature in play. Seems pretty certain that I'll win, right? Well I guess my opponent though so because he refuses to move past his main phase. It's been at least 15 minutes now and here we sit without the game having moved a bit.
I can verify that nothing is frozen, I can still select cards and zoom in on them, pull up menus, even hit the guide button and use the functions there. Right above the grey bar with the current phase in it there is a white bar that slowly depleted, which I assumed was a turn timer. Once it depleted though it refilled and nothing has happened.
Will this issue be addressed soon? It's rather unfortunate that poor sportsmanship is causing a need for the game to be "corrected", but alas you can't control other people.