Extruding vertices is only conforming to axis

I am using blender 2.5 alpha 2 and I am trying to model a gun. I started with a picture as my background and then a plane because I panned on extruding it later. When I select a vertex and push ‘e’, it will let me extrude but only along an axis. If I select two vertices and do the same thing, I am free to move the new vertices wherever i want. How do I get this freedom with only making one new vertext at a time?

Once you press e, press Esc.
The vertex has been extruded but is at the same position.
Now press G to move it.