I have this issue as well. Campaign, Steam Workshop content, and the editor all play brilliantly. However, whenever I join a server the game stops responding with no error message. It only happens while loading, after joining the lobby and picking a slot. I've gotten it to work by installing the dev build, starting the game up and shutting it down, and reverting back to the stable build. But it only works for a short time. It seems that if I restart my computer whatever is broken breaks again and I have to repeat the process.