Recently I did upgrade my Internet Explorer to 8 Release. The IE is great, but I never imagined how bad the effect would be on Sametime.
Another discovery after that, Sametime is directly dependent on your default browser for rendering the chat sessions into a window. It showed a very weird behavior of not able to wrap long chat lines in the sessions. So horizontal scroll shows up for those long chat lines. The chat sessions became more and more annoying if I have to read it with scroll over a scroll (I blame it on people who like to write essays in Chat windows).
I found a link at IBM site which need you to modify a CSS file under notes folder and it sets up everything.