Preview Shows Polygon Reference Clip as Rectangle Clip

I have a file that originated in AutoCAD 2007 that has a Layout and a Model making a Sheet. In V8 and V8i, the file looks correct in the view, the plot preview and the plot output. The layout is 3D by the way.

In XM, the polygon clip boundary (that will eventually return to being a viewport) loks correct on screen and in the output, but in the plot preview (both small and large) shows the clip as the limits of the bounding rectangle of the clip element.

Is this a known bug?