Hi,
I also use v6.30 with D7 and I am experiencing a similar problem.
After I maximize, minimize, restore, maximize (a few times), minimize button doesn't work (happens when the window is maximized). Actually it looks as if it doesn't detect the mouse release and button is displayed pressed. At the 3rd click (and release) minimize button works.
Edit: Happens when both AllowGlowing and ExtendedBorders are set to true.
Cheers,
Borya