I've only had this occur in A2 and only in "dungeon" areas. Not caves, only the dungeons (where you find Zultan Kulle's bodyparts, etc) does this seem to occur. It occurs when using dashing strike, but does not make your character flash. You're unable to attack, but seems that potions can be used, heals can be used, AoE type (sweeping winds) abilities can be triggered and your bubble can be used. 7 Sided Strike WILL break you out of this, but it will KILL you. This isn't a big deal for SC, but considering I lost level 57 HC monk to hitting 7SS I was pretty pissed off.
Blizz, can you either:
A.) Fix the bug. It's been in work in some sort of manor since Sept and minimum since early Nov (blue responded to thread).
B.) Offer a method for HC players to petition for loss of character due to a BUG which has 0 to do with lag, connection, player error or any other thing that I can control. I.E. Your coding killed me.