Update: tested on vanilla ArmA II, same problem. When I opened up the firewall log viewer, I got an entry of arma poking the cfplogvw.exe process.
@kklownboy: I know what the process is. I'm running the free version of comodo firewall. And arma IS accessing cfp.exe's memory. For obvious reasons, comodo doesn't like that (how many fw/HIPS programs _don't_ have a self-defence module these days?). I tried setting the policy for the relevant processes to allow arma to access memory. Log spam stopped, stuttering remains.
If this is the BattlEye client poking around looking for trainers/other software used to cheat in ArmA, isn't it possible to whitelist certain processes? Personally I don't like the idea of being forced to positively cripple security to be able to play.