Like KB mentioned, it's hard to see what's going on from the angle of your screenshot. Let's just go over some things:

- Did you cut and select the faces from the side view? Doublecheck in perspective that all the new faces are selected before extruding. Did you accidentally extrude twice?

- Turn on your Heads Up Display (HUD) and start selecting vertices in the extruded area to see if there are overlaps and things like that.

Make sure your tool options are all reset before going through the video. I've seen sometimes where some of the shelf buttons will retain the tool's options at the time it was made rather than any changes you make so....just something to be aware of..

If you still can't figure it out, I might be able to look at the file for you later (if you're using Maya 5, anyway).