Error: Extender controls may not be registered before PreRender.

I am getting the same type of error, but my page inherits from Page. I do have an updatePanel with AnimationExtenders. This was working somewhat before I got the latest from the AtlasControlToolkit.

I found a solution. You have to call parent method in every overiden method. So in OnInit first line should bebase.OnPreInit(e);

Is there any other cause for this error? because i am not overriding any methods in the base class in the user control I am trying to implement the AutoComplete Extender.