You are describing a Java issue. If the plug in is not working (did it install? Did you get the right one?) then there is only one other answer. The browser. You may have Java turned off in the prefrences for it. If it's on then it may be corupted, get a new copy of the browser or try a different one (IE or Netscape).
Also, Can you enter Yahoo chatrooms? If you cannot the issue is on your side and not the TMF's room.
Myriads