That happened to me yesterday too. We showed up 45 minutes early but they were already sold out. By the time we got up to the window, we decided to watch "Click" instead, and bought tickets for the 10pm showing of "Pirates", since we were pretty sure that the 7pm would already be sold out also (or really crowded). We loved "Click", so it was really worth it.
Oh boy, Pirates was great. We didn't get home until nearly 1am but it was so worth it. I can't wait to see the third one. Did anyone stay throughout the credits? They have a little bit more but we only knew about it because my brother heard about it online. EVERYBODY but us and 5 other people ended up leaving and missed it. No one's mentioned it here.