Subsequently issued movement commands are ignored if a unit is commanded to attack and has to move to the target to do so.

To express the bug:

1. Enter battle.

2. Tell a melee guy to attack a target that is not adjacent to him.

3. After he kills that guy, tell him to walk to a different square. He won't.

Note 0: he can still use attacks, spells, and abilities, and you can repeat step 2, but he will not move for any other reason.

Note 1: to cause the problem you must tell him "attack," and not tell him "move adjacent and then attack." In other words, right click the enemy, rather than right click the position and then the enemy.