Basic Questions About the Level Editor

[HakePT]

Hold alt and hold left click to scroll around, right click to zoom, and middle mouse to move the viewpoint. You can also take the viewpoint (the blue dot the editor focus's on) and force it off the axis for a free roam kind of mode. Do this by clicking the LT tab at the bottom under grid controls. Another thing I like to do is maximize a window by hovering my mouse over it and pressing space.
Hope that helps. Describe to me what your middle mouse button is doing, maybe I can help.

Well, the middle mouse button should move the viewpoint while holding lalt, but it just doesn't do anything at all.

Try a different mouse. I heard some have troubles with this setup, it was made to be used by the devs and as such some problems arise.