It was working fine for me two hours ago. After I took a break to watch one of my tv shows (i've left arma 3 open) when I came back to host a session to play with some of my friends it crashed each time I would click ok, before I would even get to the lobby screen.
I even went as far to downgrade back to normal arma 3 and re opt into the dev branch and still have the same crashing. I have even restarted my PC with no avail in solving this.
I think it must have been caused by a recent update or something. Since how can it be working fine two hours ago then just start crashing. I hope this gets resolved soon since it is almost game breaking since I and many others cannot host sessions to play zeus with their buddies.