Hi,
Are you sure that the correct object is found when you call NativeWebObject.Find? The condition you set there is quite general, and since you search the entire page, another object which meets the same condition can be found. In this case, if this object is hidden behind your overlay item, you will get this error.
So, first of all, make sure that you obtain the correct object by checking its FullName. As a better solution, avoid searching the entire page. Obtain the object which corresponds to your overlay item and work with its children instead of just calling page.NativeWebObject.Find to get to your button.
