Why am I unable to extrude/translate along the Z-Axis? I have a 2D mesh plane dividing into numerous faces. I have x amount of faces selected and I want to extrude or translate them along the z-axis to create a 3D model. I am trying to do this:

From the 5:30 mark to the 5:50 mark in this video

http://www.youtube.com/watch?v=mbm9lPB5GPw#t=5m30s

My object will not move along the z-axis. The faces don't move at all, even if I type in the amount to move along the z-axis and press enter, it continues to just remain a 2D plane.

I can't figure out if I have a setting turned on or off that is causing this or if its something else. It seems it should be straightforward, but I have not been able to solve it.

EDIT:



I cannot get the selected faces to extrude/translate outward from the plane along the Z-Axis.

EDIT 2:

Here is my .blend file

http://www.pasteall.org/blend/29706
This is because the Z scale of the object is 0.

Apply the scale (CtrlA> Scale) or set the Z scale in 3D view > Properties region (N) > Transforms > Scale:



Then extrude/translate should work fine.