Thanks for your help! Its my mistake, I had put my canvas under update for some reason, and I let it to turn on and off continuously that's the problem.
And I have another problem it might have from my side, I need your suggestion on this error following: what makes this to throw errors like? I have instantiated a canvas pvrUIcanvas attached script, and I m giving reference to event camera at runtime. The canvas contain a button, after the button gets clicked, "UICANVASDRAGGABLEPANEL" is destroyed or disappeared, even the scripts are exist.
NullReferenceException: routine is null
UnityEngine.MonoBehaviour.StopCoroutine (UnityEngine.Coroutine routine) (at C:/buildslave/unity/build/Runtime/Export/Scripting/MonoBehaviour.bindings.cs:117)
PvrUICanvas.RemoveCanvas () (at Assets/PicoMobileSDK/PvrUnitySDK/System/UIEvent/PvrUICanvas.cs:138)
PvrUICanvas.OnDisable () (at Assets/PicoMobileSDK/PvrUnitySDK/System/UIEvent/PvrUICanvas.cs:30)