There was an attempt to perform an action on a zero-sized window

A screen shot of the object tree section you are working with may be helpful.  Expand it out to the child object you are trying to work with and include any relevant details of the objects.

I once had to deal with an object that was a TextBlock until it was clicked on.  Then it became a TextBox I could add data in.  The manual GUI tests were fine but TC had to be coded to click the 'Block' and wait for the 'Box'  A super big pain to discover and code around.