Game freezes on joining lobby

Any attempts to play with other players of any kind is unsuccessful. When joining a friends lobby, my client crashes. When a friend joins my lobby, the game crashes. When I attempt to join a matchmaking game with other players (no friends in lobby) the game crashes upon finding other players until I am kicked for inactivity, at which point the game becomes responsive again. The same issues occur with the firefight mode.
Repro Steps
Boot up game, join friends lobby, game freezes. Open Task Manager - End Task. Start the game from steam, click matchmaking, select desired playlist (Big Team Heavies in Reach), select start, game crashes on trying to join lobby, wait several minutes, booted for inactivity.
Repro Rate
Always (100%)

Issue is still occurring, even after changing frame rate cap to 60, and enabling V-Sync. For some reason I was able to get a game in earlier, doing BTB on Reach.