If that is what you got from my previous reply, my apologies, as neither case would be my interpretation and my explanation must not have been clear.
For the standard version of the spell...
The mounted knight could continue riding, just nothing fancy and no initiating new actions. He would be able to even attempt a parry (at half OB).
Casting on the horse would lead to the horse slowing his pace until he is traveling at a walk.
A flying griffin in a dive attack would end up doing a "fly by" - no attack - and would continue to remain aware of the foe (now behind him) and probably loop around.
Free climber standing on a mountain ledge simply remains standing there. Hanging on the side of the mountain remains hanging there - stops moving.
For the increased confusion version....
Knight - simply holds onto his mount to keep from falling off, at a loss of most of his DB benefit.
Horse - Quick slow to a stop, knight needs to make a riding check (Hard) to remain on his mount.
Griffin - in a dive attack - make a hard flying maneuver to avoid flying into the ground (assuming target is on the ground), if successful just a fly by (but no consideration for foe after the fly by)
Climber - remains standing on ledge or if his position is precarious to begin with, allow a hard check to see if he can hold on - but he won't be moving.
Sorry if my previous explanation led to confusion.
