This happens from time to time.
Sometimes helps to tweak the "Perspective" setting a little bit.
Sorry for ommitting some details.
I had tried a range of Prespective from 0° to 90° and extrusion depth from 10 to 100 with no difference in what faces are created. This has been over a period of several weeks so Illustrator has been launched many times and the MacBook Pro has seen a couple of reboots.
This is on an MBPro 2.3Ghz i7 with 16Gb of RAM and MacOS 10.6.8.
try changing the Y axis to 1
Bingo, Ton. Angling the Front face ever so slightly got the extruded faces to display. Even 0.1° was enough.
Actually, .01 is enough.