(Ubuntu 15.04) GMod freezes when clicking the 2 player option

So, when my friend and I are wanting to play together, when I click the singleplayer drop down button, and click 2 players, it freezes forcing me to force close GMod.

He is on Ubuntu 15.04 aswell, and it freezes when clicking 2 player also.

Please fix this because I have it portforwarded so when it is fixed we can just play it.

It also kinda sucks because I want to play with my Sister on a lan world.