Everyone appears to be invisible and my head is stuck in the ground.

I just bought Garry’s Mod; I know I have the correct system requirements as I don’t lag at all. I have Team Fortress 2, Portal:First Slice, and Half-Life 2 installed.

This is what it looks like:

For some reason it works on singleplayer, but it won’t on any multiplayer servers. Help?

Nevermind I fixed it. It was a add-on.