I'm glad this thread resurfaced; I couldn't find it yesterday.
So I'm fighting Svala on heroic yesterday and IT happens. The main screen just shows the shamans all standing mid-cast, the sword is hanging about 10 feet over my head, but the other screens are fine.
I end up biting it and really can't recover. Svala wipes my group with 2424 health of her own left. This really belongs in my multiFAIL thread.
I have no idea what caused one window (all 5 on same computer) to have intermittent packet loss for about 10 seconds (right as my tank was being sac'd too). It sucked because even with killing all the adds the sword still got her because I couldn't move.
No matter how many times I hit the "OMG RUN" button.