First Person Camera switching

I am using the built in 1st person controller and am trying to script for a camera change from the player camera to a world map camera when I click a Gui texture, using this script:

var camera1 : Camera; 
var camera2 : Camera; 
function Start () {     
    camera1.enabled = true;     
    camera2.enabled = false; 
} 
function OnMouseUp () {     
    if (camera1.enabled == true){         
        camera1.enabled = false;         
        camera2.enabled = true;     
    }     
    if (camera2.enabled == true){         
        camera1.enabled = true;         
        camera2.enabled = false;     
    }     
}

This is not working however. I am getting the world map view, but it does not change back to the player camera when I click the GUI button that the script is attached to again. I think it is because the first person camera is not disabling, but I am not sure. Please help.