GUI.Button lags on iPhone

I'm testing this on a clean project without anything in it and I'm still getting this strange lag. I have created three buttons like this:

         void OnGUI() {
                 if (GUI.RepeatButton(new Rect(10, 500, 120, 120), @"One"))
         goLeft();
     
     if (GUI.RepeatButton(new Rect(Screen.width - 120, 500, 120, 120), @"Three"))
         goRight();
         
     if (GUI.Button(new Rect(Screen.width/2 - 60, 500, 120, 120), @"Two"))
         TapFunction();
 }

The thing is, when I tap on the button, then release the finger and quickly tap on another one, sometimes the button is not quick enough to respond. I have to wait for some milliseconds after releasing the finger so that I can tap on another button. And this drives me absolutely crazy. I'm using Unity 4.0.1, iOS 6 and Xcode 4.5 Any ideas on what it might be? Thanks.