had the same prob in pvp1 today
it was not my turn, so i wasn't really paying attantion to the screen.
i can't tell you if my opponents time was over or this just happens randomly, but i lost and still had hp left.
Edit: just happend again. This time it was my turn, after my opponent lagged out and computer took control. i got the message: your connection to the server is not responding, you wil loose this game in 5 seconds.