We have the same issue. We checked the technotes below as proposed by IBM support, we restarted the server 50 times, however we did not manage to solve the issue :-(
We do not use SSL yet. We do use tunneling. We did specify the fully qualified host name in the properties file. The servlet also replies when I directly type it's URL....
Title: Presentation slides do not load in Sametime 7.5 meeting
Doc #: 1246117
Title: Slides do not appear or tab is grayed out in Sametime Meeting Room Client
Doc #: 1252934