Maya 2011 trouble

[bumblebee666]

im a maya newbie..in maya 2011 i could rotate using (ALT+ LMB),pan using (ALT + MMB) and zoom using (ALT + RMB) but suddenly something happened and i cant seem to do it anymore...did i press some shortcut key to disable these features??...please answer to the point.

 

[nikorr]

Only on one file or all of them?