While in the XClip menu make sure F6 Ignore Z is turned on. Xclips will sometimes clip out things if their zheights are abnormal. With Ignore Z on, it will display everything within the xclip regardless of it's Zheight.
Thanks! - Josh Do. Or do not. There is no try. Josh's Digital Downloads is come back online soon. Stay tuned. (soon is a relative term)
Right, we typically use Clip Cubes in 2D - but they are 3D Clip Cubes; so as Josh mentions, it could well be a stray Z height that is affecting what you see.