Lync 2011 Mac cannot write into shared desktop sessions

Hello.

Recently our organization initiated a beta test for Lync (switching from Communicator 2007). I am currently the only Mac client included. 

The problem I have is that although Windows users using Lync 2013 or Communicator can share their desktops and I can have control of the cursor, I cannot write into the shared session. Its not the UAC dialogue. I cannot write in any text field anywhere. Naturally in Communicator for Mac I could.

Thanks so much for the help!