Thanks Jason for the reply. Actually, this seems to only happen if my uir is not already open. If I open the uir before using the Get UIR Object function, I never have this problem. So this is usually what I do, but occasionally I don't realize that my uir is not yet opened, click the icon to Find UI Object, and get the error.
My project is quite large, but if that is the best way, I'll send it.