MOZILLA FIREFOX PROBLEMS: White Box and ActiveX

I use both IE and Firefox, but Firefox has developed two major problems, perhaps related to each other: (1) No matter what URL I go to, a large rectangular area is white--i.e., nothing at all in that space. It is always in the upper left quadrant of my screen; (2) the full color and graphics do not come up in any URL. I'm guessing it is an Active X-type problem, but no one seems to to know what to do about it.

(1) Any solution?
(2) Can I uninstall FireFox and not lose my settings (Bookmarks, etc.)?
(3) How do I make IE my default browser?

Thanks!

Involved1 (aka David)
grinch2171...I really appreciate your help on the questions I've posted over the last day.