Alright, so VALVE decided that, "Hurfadurf I'ma urpdate surce while gury on vacotion." So now Gmod got fucked up and you can't connect to the server. Blame Valve, not Gary. Anyway, here's a quick fix for you guys.
When starting Garrysmod, enter console, you all should know it, it's the ~ key. When it's open, type in vgui_allowhtml 0, the problem with Garrysmod was that anything involving the internet, multiplayer side, half life had missing code that didn't understand and was like, "Does not compute," and shut down.
Enter this in, should work for you, and I hope to see you on the server.