Hover make Sprite disappear in Grid scroll view (Dynamically created sprite NGUI)

I have made a scroll view and using Grid to arrange sprites.
I add sprite dynamically ,by using prefab.
Sprite items create successfully but when mouse hover sprite applied by code disappear and original sprite appear … help to get rid from this problem …

public GameObject RootGrid;
public GameObject ItemPref;
GameObject Obj;
// Use this for initialization
void Start () {
	for (int i=1; i<=12; i++) {
		GameObject item=NGUITools.AddChild(RootGrid,ItemPref);
		item.name= "item"  +  i;

   RootGrid.transform.parent.GetComponent<UIScrollView> ().ResetPosition ();
	RootGrid.GetComponent<UIGrid> ().Reposition ();
	Debug.Log("Child Objects: " + CountChildren(transform));
	Debug.Log ("From Add Child Script");

int CountChildren(Transform a)
	int childCount = 0;
	foreach (Transform b in a)
		foreach (Transform c in b){

			UISprite yourSprite =Obj.GetComponent<UISprite>();
			yourSprite.spriteName = "NGUI";

		Debug.Log("Child: "+b);
		childCount ++;
	return childCount;

UIButton component was making problem …removing it provide solution…