Hello I'm having this problem, too. It looks same like Chevy90's video:
I'm playing like 2 - 3 hours on any milsim server, everything is fine, 28 FPS stable (more less :) ) and then, suddenly, fps drop to 1 - 5 FPS, graphics details will instantly get lowered (it looks like 15 years old game), ballistic carriers will fly under soldiers, etc.... After pressing Esc button, game freezes and then appears error (something like: "The instructions at 0x ....[numbers and letters] .... referenced memory at ... [numbers and letters] .... The memory could not be read.").I will try to make screenshot of that error message after next game crash. I've noticed that FPS drop comes after spawning new units (new task appears on map, reinforcements, ...). I've tried lowering graphics details and distance and it didn't help (lowered to Low, to Normal, to High, nothing has changed). I'm not sure, but I think that same error has been occurring to me in ArmA II OA when playing MP on Ultra details, lowering to High solved this problem (I was playing at same device, no change). My Hardware: CPU: Intel i7-471MQ (~2.5 GHz, auto-overclocking at ~ 3.2 GHz, 4 cores)
GPU: nVidia GTX970M RAM: 24 GB
HDD: 1 TB (currently 120Gb of free space)
Cooling is fine, temperature after fps drop ~ 60°C When playing SP, graphics details are set on Ultra and no problem, in MP I'm playing at High details (distance set to 2km on foot, 3km in vehicle, 5 - 12km airborne). Mods: CBA, ACE, CUP, TFAR, RHS, Blastcore, JSRS and some more (25 mods total)