Well, since I solved my own problem, I thought I'd post the fix in case it helps others with any similar troubles. My problem in Facebook was a blank window when there should be text. (a list of names) The culprit I think was when I "upgraded" to Firefox 4, not all of my settings came along for the ride. The fix was very specific.- I right clicked the blank window. Selected "This Frame", selected "Frame Info" to see what it was and what it wanted. A window pops up about that frame. I selected the "Permissions Tab". It showed the permissions for this website and its troubling window. It told me the popups and add-ons were blocked. (I had them set to allow for this site on my older version of Firefox.) So I copy/pasted the address in the Permissions window (in my case- www.connect.facebook.com) into the Allow Popups and Allow Add-Ons for this site sections in Options in Firefox. I also noticed in the Permissions window for Cookies that the "use default" box was clicked and that the "for this session" was greyed out. I unclicked "use default" and that turned "for this session" back on. Somehow, even though Firefox is set to allow cookies for a site for a session, this frame wasn't getting that message. I had to manually go in and set that. But all this worked. I righted my settings that got deleted in the upgrade and I had just forgotten about. (there are probably others for other sites that I will just stumble on later) And fair warning and full disclaimer- I'm no tech, just frustrated and stubborn, but going into the trouble and monkeying around, one click at a time, armed with basic understanding only, seemed to work. If it's one particular spot that's giving you trouble, I say give it a go. And good luck.