Hi
I had the same problem - I think you are using the classic browser client which is not included with sametime 8.5 - I had to download the client "javaconnect.zip" and unzip it into the
...\Domino\data\domino\html\sametime directory
javaconnect can be found in this URL (this may move)
http://www-01.ibm.com/support/docview.wss?rs=203&uid=swg21243158