Noticed that someone had reported this for Chrome or one of the other non-MS browsers and status is now "fixed".
It is broken for my PC/WinXP/IE8.
I can get the focus to the chat but the floating ad covers up about the first 12 characters of the chat window. Can't see usernames and if the chat is more than one line can't see the start of the second line.
Your attention to this defect is appreciated.