3D render problem - Parts missing!

[Pocket92]

Some (well most) objects are not showing up for my render
Whats causing this?
This is the only drawing this is happening for. It is very complex
Pics speak better than words

http://upload4.postimage.org/cars/triadfbody/971325/1.html

http://upload4.postimage.org/cars/triadfbody/971326/2.html

http://upload4.postimage.org/cars/triadfbody/971330/3.html

AutoCAD 2002 full version
Ive got plenty of mojo computer-wise
Any ideers?

Additionally the whole drawing has alot of large value meshes
Is there a more simple way to generate solids that look like this without the blocky mesh2solid lisp?
Maybe a lisp that alows you to slice solids using a mesh/surface rather than 3 points?

Jon ~