Just doing some reading the third umpire might have been right in the Morgan dismissal.
The MCC changed the definition of grounded in 2010 because of the ability of TV to go frame by frame. Now I thought that it was changed to being grounded at all but it states the foot only.
http://www.lords.org/mcc/laws-of-cricket/laws/law-29-batsman-out-of-his-ground/
1. When out of his ground
(a) A batsman shall be considered to be out of his ground unless his bat or some part of his person is grounded behind the popping crease at that end.
(b) Notwithstanding (a) above, if a running batsman, having grounded some part of his foot behind the popping crease, continues running further towards the wicket at that end and beyond, then any subsequent total loss of contact with the ground of both his person and his bat during his continuing forward momentum shall not be interpreted as being out of his ground.