Win7 elo Touchscreen GetMouseButton TimeDelay

Hi

I'm using Unity3.5 Win7 and an elo Touchscreen.

While using Input.GetMouseButton I press the Finger onto the touchscreen and then I have to wait 4 or 5 seconds until Input.GetMouseButton reacts.

Example: I add this script to a cube:

 using UnityEngine;
 using System.Collections;
 
 public class ChangeColler : MonoBehaviour {
 
     Color cDefault = Color.green;
     Color cActiv = Color.red;
 
     Material myMat;
 
     void Start () {
         myMat = renderer.material;
         myMat.color = cDefault;
     }
 
     void Update () {
         if(Input.GetMouseButton( 0 ))
         {
             myMat.color = cActiv;
         }
         else
         {
             myMat.color = cDefault;
         }
     }
 }

After pressing the touchscreen I have to wait 4 or 5 seconds until the Cube changes the Color.

I have the same Problem with GetMouseButton and GetMouseButtonDown.

I don't have this delay while using the mouse. (instead of the touchscreen)

Any idea of getting rid of this Timedelay?

Thanks.