Without further information or knowing exactly what it is that you did to cause this to happen (yeeeesss, unfortunately most common errors in Maya are caused by user error. Pressing the wrong hotkeys, double clicking, accidental menu selections within the hotbox, etc.), try this:

Go to C:/Users/Documents & Settings/(User Name)/My Documents/Maya/(version #) and delete the PREFS folder.

This will reset Maya's preferences back to default. If you have any custom shelf items, marking menus, etc., then you might want to copy those respective folders from the prefs folder before deleting it.

Give that a shot.