Google seems to have changed some of it's coding for their personalized
homepage service (as least as far as I can tell), and now when I try to
extend the "Add Content" tab it opens, but then after it finishes
loading it collapses again (by force, not smoothly). I have not
changed any settings on any internet-related software since I last used
the Add Content feature and am currently using the latest version of
Firefox (1.5.0.1) with no other pop-up/under/sideways programs. J/W if
others are experiencing this problem or if it's something special to my
setup, thx =).

I am experiencing exactly the same problem!