Can't use skills sometimes (in BGs)

i know a myst that had the problem too. he reported: a few times in canyon and a few times in corsiar. also you can not see the other players and still can be tapped, touched or knocked by enemies. at the end, the char is dead on the ground although the opponent has hit a very different end of the map. one time he got knocked by an invisible char. after dead he teleported to the right position of the map.