The Crash happened to me a few times on Official Co-OP MP missions.

Now that I did my temporary fix a few times though, my ARMA III game is running fine with little to no crashes for around a day now.

Yes Russian, it did work for me. My game still crashes once in a while though, so I have to do the fix all over again every now and then.

I agree Overmind. I think we shouldn't have to rely on temporary fixes for a bug this bad.

You don't NEED to back up your files because really all it is in that folder is custom server sounds, Cache for some Multiplayer Missions, and a few temporary files.

After you delete the folder, next time you load up ARMA 3, it should make a brand new folder for you. the only reason why I say to back it up is due to any saves in Multiplayer MIGHT be under this folder.

All I can hope for now is a fix for this game crashing bug.

Before you do this fix, make sure you BACK UP YOUR FILES. This is a TEMPORARY fix for me, and it may not work for everyone.

[POSSIBLY A TEMPORARY FIX]

When I go into into my directory for ARMA 3 Alpha under
C:\Users\<Username Here>\AppData\Local
And delete the "Arma 3 Alpha" folder, the game should start to work next time you load up a multiplayer match.
Just remember for everything to load in the game and take it nice and slow.
If you get the same error again later down the road, just delete the folder again.

\\Bohemia Interactive, try to keep this report alive until there is a permanent fix to this crash. The steps I listed above are just temporary for now so people can at least play the game. No consumer should have the trouble of going through this game breaking crash.

I'm getting the same crash also.
I hope someone finds a solution on how to solve this soon.