At work, they replaced my HP ProBook 6450b with an HP ProBook 6470b. This upgraded my video chip. (It wasn’t something I wanted. They just do this every 3 years as a “lease roll”.)
This broke my DisplayLink adapter. Mouse was almost invisible, often left mouse droppings, and window update was abysmally slow. I knew this wasn’t USB 2.0 slowness, because the same adapter worked on the old laptop.
I don’t know why, but changing from the Windows Classic theme to the Windows 7 theme made it work. I’m guessing they don’t do much testing with the classic theme, and there’s a bug. I don’t really care for the Aero look, but it is better than a broken mouse pointer.
Note that it does not work with Windows 7 Basic.
DisplayLink hints that this might be the case: http://www.displaylink.com/support/ticket.php?id=260