There is a hotkey for soft selection mode. I believe it is the "b" key. Chances are you or your son inadvertently pressed it. Just mentioning this in case it happens again. I had a similar experience. I was adjusting the brush size and pressed "b" without holding the middle mouse button down.
While on the subject I wish autodesk would incorporate modo style falloffs and selection capabilities. They are far superior to maya's.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
Last edited by ctbram; 28-10-2010 at 03:37 PM.