I have tried minimizing the box in IE9 & Firefox, but it only stays minimized for that page only.
Every time you go to a different page you need to minimize it again. It doesn't minimize globally for me, just the page you are on.
EDIT...just noticed that if you minimize it while on the forum home page, then it does minimize it globally. If you do it on any other page, then it minimizes for that page only.