I have a very simple OpenGL 3D scene that I'm trying to render that contains 2 semi-transparent boxes, one in front of the other. I'd like to render them with glDepthMask turned on and with the boxes rendered from back to front as suggested here: http://processing.org/discourse/yabb_beta/YaBB.cgi?board=OpenGL;action=display;num=1210475303;start=2#3. (I want to render the scene with glDepthMask on because this is a test for a more complicated scene)

The problem is that the objects do not display the way I expect. I would expect them to display in exactly the same manner as if I had glDepthMask turned off. My draw method contains the following code:

-------------------------------------------
background( .85f );
camera( 0, 0, 200, 0, 0, 0, 0, 1, 0 );
fill( .5f, 0, 0, .5f );
pushMatrix();
translate( -70, 0, -100 );
box( 100 );
popMatrix();
fill( 0, 0, .5f, .5f );
box( 100 );
-------------------------------------------

Are there additional OpenGL calls I need to make in order for these cubes to display correctly?
Thanks in advance for your help.