GUI Buttons Not Displaying

I have tried in both Unity 3 and Unity 4, but neither will display the GUI buttons.
I am following the remixgames FPS tutorial, for anyone wondering.
Thanks.

This is the code:

using UnityEngine;
using System.Collections;

public class MenuManager : MonoBehaviour
{
	public string CurrentMenu;
	
	void Start()
	{
		CurrentMenu = "main";
	}
	
	void OnGui()
	{
		if(CurrentMenu == "main")
			Menu_Main();
		if(CurrentMenu == "Lobby")
			Menu_Lobby();
		if(CurrentMenu == "Host")
			Menu_HostGame();
	}
	
	public void NavigateTo(string nextmenu)
	{
		CurrentMenu = nextmenu;
	}
	
	private void Menu_Main()
	{
		//Main Menu Buttons
		if (GUI.Button(new Rect(10, 10, 200, 50), "Host Game"))
		{
			NavigateTo("Host");
		}
	}
	
	private void Menu_HostGame()
	{
		//Buttons for Hosting
		if (GUI.Button(new Rect(10, 10, 200, 50), "Back"))
		{
			NavigateTo("main");
		}
		if (GUI.Button(new Rect(10, 60, 200, 50), "Start Match"))
		{
			
		}
	}
	
		private void Menu_Lobby()
	{
		
	}
}

Change OnGui() to OnGUI().