Ah-ha! In the javascript window almost every section has a line in red with an 'undefined' type error.
Yes, I use AdBlockerPlus. I just disabled it for the site, the appearance of the page changed to the way it looked when I first opened the new account (there's a purple background) AND the javascript errors disappeared.
After a second or two, or maybe I refreshed the page, the state reverted and the js errors returned.
I can post the javascript if it's helpful but I think it only pastes in in black!
(This is in Firefox on a Mac)