Hi, I recently encountered the same problem. Ampersand is not working, neither is Shift-9 or Shift-Del. The shift keys are WORKING, the 7, 9 and Del keys as well, just not in their three specific combinations. I have a MS Comfort 2000 keyboard that has functioned without any problems so far, and I have no other software running that might steal keyboard shortcuts.
The only clue that I have found online is that it might have something to do with the multimedia buttons on the keyboard; I rarely use the Play/Pause key but a few days ago I did. Can't seem to undo whatever it is that that button might have done, resetting the keys to their default behavior did not help at least.
Have you (or a third party program), possibly switched the keyboard language? Hold the left "Alt" key and press the left "Shift" key, and then release them. This changes between languages. Then try the & again. If this is succesful, you can check your keyboard language settings. Control Panel - Regional and Language options.