In ACA 2010 if I raise my cut plane up to a point where it no longer cuts
through a door window assembly, the frame disappears but the door part of
the assembly is still displayed. Regular doors don't do this, just
assemblies. Same condition in 2009 behaves as expected, ie if the cut plane
doesn't go through it, it doesn't show. Am I overlooking something or is
this a bug?
Yup, that's broken, but if you turn off 'Use cut plane of containing object when anchored' in the plan display rep of the door/window assembly it works. Go figure.
Have you logged this with your Adesk vendor, or posted it to the Adesk support site?