This scenario happened in our 4E game last night. A Troll (2x2) started in a non-threatened space and tried to move 2 squares to attack the cleric. With the first step, it entered a square threatened by the striker. With the next step, the back of it's body still occupied the threatened square but the striker argued that she got to make an opportunity attack. In my opinion, the Troll was not leaving the threatened square and therefore, did not provoke?
Does the troll provoke an opportunity attack on step 3?
('T' is the troll, 'R' being the player)
TTx xxx xxx TTx -> TTx -> xxx xxR TTR TTR xxx xxx TTx
What about here? (The threatened square being 'A')
TTx xxx xxx TTx -> TTx -> xxx xAx TTx TTx xxR xxR TTR