HCL Sametime Forum : [Solved] Sametime 9 Connect: Sametime cannot connect to the following meeting room server.

Hello,
After installing Sametime Client on several PCs, I realized that some of them have trouble connecting to the meeting room server.
The following message appears after an attempt: "Sametime cannot connect to the following meeting room server: MEETINGSERVER.com" (Meetingserver.com isn't our actual server, it's just a placeholder in this example.)
It is possible to log in using the client, we're able to chat with each other, but when it comes to checking the meeting rooms, no dice.
All computers have the same configuration when it comes to the meeting server, but for some reason, some people can access the meeting rooms, while other can't.
Yet, meeting rooms can be created through any web browser, by any user.

The workplace I am in doesn't host the server nor has access to its configuration; it's all done by a third party enterprise, so I can't really check the server activity by myself. Still, I get ping replies from any PC.
There was a similar issue on this forum, but the solution featured involved installing the Web Plugin, which is already up and running on most of our machines.

Any ideas on what could cause this problem? Could it be a problem server-side? Maybe due to its configuration?
Thanks for your help.