I just left a comment in another thread about this issue, but that thread is marked solved so I'm afraid the powers at be might not look at it.  However, this solution only opened up another bug as I've described here:

http://forum.jquery.com/topic/ui-widget-overlay-css-selector-causes-consistent-large-memory-leak-in-ie#14737000000749340

I hope this gets fixed before the final release or I'm guessing we'll have some unhappy campers.

Maybe the solution is to not have this line in both the destroy and close methods for the dialog:
(self.overlay && self.overlay.destroy());