I have a MacbookPro running 10.6.7 and my dock is on the left side of my screen. I also have another screen attached via thunderbolt VGA adapter.
I start Designer 2, build 268, click "continue my trial", click "Ext JS 4.0.x", and find it's over my dock. I press the green + sign to have it fill my laptop screen, which fortuneately no longer covers my dock.
However, when opening a project, it slides back over my dock and no longer fills the screen.