If a GOverviewMapControl is added and removed from a GMap2 object, it causes an error when checkResize() is subsequently called on the map object. Hypothesis: it's still connected to an internal onResize event. The error occurs when trying to access the parentNode of the overview map div, which is null because the control is not in the map anymore.
Clock "Toggle Size" and after the overview map is first added and removed (ie. 2 clicks), watch errors occur on subsequent adds (3rd/5th/7th clicks).