Problem with Live Session when is accessed from internet (in LAN work)

[teodor]

Hello!
We have installed Learning Space 5.0 Core Module and Collaboration Module in the following configuration:
Windows 2000 Advanced Server (with Service Pack 2 installed)
IBM® DB2® Universal Database 7.2 for Windows 2000 Advanced Server
The system works very well in the LAN and we can use all of the facilities offered by the Sametime server from Collaboration Module, that means chat, whiteboard, share of an application and audio/video.
When I try to access the server from internet, I received the following error when I’m in the “Live Session”:
“There is a problem with your classroom.
Contact your system administrator”
The server is outside of the firewall, so all of the necessary ports are open.
When I access the “Live Session” it opens but the whiteboard not loads. It remains gray and writes “Loading”. Also the sharing of an application and the audio/video not
working. The rest of the function, Chat, Follow me and Q&A works good.
Please tell me, are any special settings of the Sametime server, for that will be accessed from internet?

Please HELP ME!!!