cheesyapocalypse

Every time I try to load up multiplayer it crashes. When I join my friend's game and when I host a game, it doesn't matter. Single player works just fine, it's only multiplayer. It's been doing this for months now, I've tried several different fixes from stuff online. I've uninstalled and reinstalled the game, my graphics driver is up to date, the game is set as an exception in my anti-virus, and I've verified the integrity of the files several times. If anyone has any ideas on fixes that might work, I would really appreciate your help.