I've had this problem for a few days and it seems that it is the recent patches that has caused this since I used to be a heavy Arma player then I switched to counter-strike for a while then after coming back to arma I run into this issue.
I have a i7-4770k processor clocked at 4 GHz with a H80i cooler, and recently when joining any server on arma 2 oa (this includes mods such as dayz) my cpu usage is about 20% when joining, then when in the lobby it goes to 0% and arma 2 oa freezes and wont let me do anything so I have to ctrl+alt+del to exit. Additionally when I go onto server browser my cpu usage on arma goes to 100% then crashes.
I have all ready tried re-installing the game and mods multiple times, updated drivers, run as administrator and launch parameters to set cpu cores and memory usage.
If anyone can help/give suggestions that would be greatly appreciated.
EDIT: Single player/armory works fine with no issues or lag and it is only in game lobbies that this weird lag is happening