I cant kill the monsters after level 13 ( Dits V16 / LTD v17)

I can not kill the monsters after level 13, my character gets lag and this stops attacking, while the monster keeps hurting me!

I use the REV 5.3 fix and also tried the REV 5.1

http://www.youtube.com/watch?v=QjDmkJY3VYI