The zoom function with the mouse wheel sometimes zooms uncontrollably I do not believe the reference question about zooming to a point and refusing to zoom further relates to what I experience.  When I open a file, one click either way on the mouse wheel zooms + or - approximately as much as one click on numpad+ or numpad-. After working with the file for a while, zooming with the mouse wheel is no longer useful: one click of the wheel changes the image from microscopic to huge or the reverse. Numpad+ and numpad- continue to respond properly. It is especially bothersome when I depress the mouse wheel to inspect an element in 3D mode. It is hard to depress the scroll wheel without rotating it a little.  Just a little rotation makes the selected element almost disappear or become huge.  I'm using Blender 2.72b.
I recently had this same problem in Blender 2.72 with no apparent answer. However, I found that by pressing Shift - C re-centered the Viewport and then I switched from User Perspective to User Ortho with NumPad 5, and everything returned to normal. I too experienced uncontrollable zooming that led to unquantifiable Location coordinates, but this method worked for me, I hope it solves your problem.