first, confirm this isn't a setup/model problem
close all models
tools > options > systmes options > performance > enable software opengl
does it get better? start playing with drivers.
build a simple tube, run it, see if it works. if it does, its the setup/model on your other problem. upload here for diagnostic.
tube doesn't work? contact your reseller. something is broken with your install or software.
Jared, You were right(!), it was simply a display issue. Somehow I had made the cavity walls opaque.