Sprite-button being pressed when not even pointed

I've made sprite-button with OnMouseUpAsButton() and all that stuff that calls method on menu object that draws menu with OnGUI() methods. And it works Ok except one problem: when I press GUI-button that closes menu (sets "opened" flag to false stopping menu drawing) the sprite-button is being pressed again opening it. I've checked everything: I'm absolutely sure that sprite-button's OnMouseUpAsButton() is being called again even it is not pressed. Any ideas?

Ok, here are some strings:

     public class StoreButton : MonoBehaviour {
         void OnMouseUpAsButton()
         {
             GameObject.Find ("Shop").SendMessage("Open", gameObject);
         }
     }

And that's a part of menu code:

             public class Shop : MonoBehaviour {
                 private bool opened = false;
     
                 void OnGUI()
                 {
                     if (opened == true) {    
                                     GUI.Box (new Rect (x, y, 650, 650), "", "Box");
                                     toolbarInt = GUI.Toolbar (new Rect (x + 7, y + 12, 636, 41), toolbarInt, toolbarStrings, "button");
                                     switch (toolbarInt) {
                                         case 0: break;
                                         case 1: break;
                                         case 2: break;
                                         case 3: break;
                                     }
                                     if (GUI.Button (new Rect (x + 315, y + 557, 157, 66), "Продолжить", "continue"))
                                             Close ();
                                             
                             }
                 }
                 void Open(GameObject caller)
                 {
                     opened = true;
                 }
     
                 void Close()
                 {
                     opened = false;
                 }
         }