When trying to orbit view, the drawing swings wildly off of the screen.  It doesn't disappear behind any clipping planes. Zooming far out, in plan view, it looks as though the center of the orbit is very high on the z axis.  A small move outside of the orbit circle moves the part/view vary rapidly.  The drawing is centered on the orgin.  I've not been able to find out how to change the center of rotation, or if that is really the problem.  Any help would be appreciated.