Hi.
Since I did the upgrade from Version 6 to 7, I encountered stuttering and laggs in Arma 2 and 3 (only in multiplayer!). My first thought was, that Windows 8.1 causes these problems, but both games run perfectly on a fresh 8.1 installation.
Today i've noticed that Eset's Advanced Memory Scanner, which is part of the HIPS, causes the game to stutter. By deactivating it, both ArmA 2 and ArmA 3 run fine.
I found this Video on Youtube just to give you an idea on what I'm talking about:
https://www.youtube.com/watch?v=Dd9NEYOVqwM
with best regards,
marvellous. (wondering when it will be fixed)