I've seen a number of vanguard + archenemy games with 8 players (and, by the way, it's
freaking awesome that these games are even possible) get stuck when an opponent is reduced to 0 life due to life loss or paying life (but not from loss of life caused by damage). I've seen this happen with a number of different cards (most recently
Bubbling Cauldron), and I believe it's been reported by others with cards I haven't used. I've seen it happen in both the upkeep step and the end of turn step. There is no error, exception, or crash, and it's still possible to hover over cards to change the card preview, but pressing enter or clicking the OK button does not pass priority, so there's no way to continue the game.