Do you mean ground unit moves? You are in the ground phase and you select a unit and you move the cursor, but when you right click nothing happens? This can happen when a unit is frozen but was accidentally given MPs for the turn 1 start of a scenario. If you hover over the unit, and it shows "Fzn #" in the rollover, than it is frozen for # turns and can't move. But this is a rare thing to find. This is the only time I think I've seen the movement path shown but the unit can't move over land.
All understanding comes after the fact.
-- Soren Kierkegaard