Illustrator :: Extruded Text Missing Faces

Trying to do a piece with plain flat san-serif text on a spiral extruding into the distance with the center of the spiral as the vanishing point. When I do this, some extruded faces are created and others do not. Usually teh curved parts of the letters get extruded but the flat surfaces (like the flats sitting on the baseline) do not. Tried both as editable test and as outlines. Same surfaces were missing.

Tested with a much simpler version - 2 lines of text with returns between them so one line was near the top of hte page ans the other near the bottom so the extrusion would use the center of the page as the vanishing point. Similar result but different surfaces were missing.
 
I know the CS suite is not meant to be a 3d powerhouse but I realy don't have the time (or money) to learn Maya or Blender or similar. I'm decent at Google SketchUp but importing eps outlined into the Pro version yields thousands of unconnected segments. Might as well draw the text by hand at that point...
 
Here's the extruded outlines - the curved parts of the letters get extruded but the flats do not:

Here's the test using just 2 plain lines of text. This extrudes more faces but lots of flats are still missing: