MSN and error 8100030d when logging in

I received this error when logging in into MSN. Looking for this error message on the Internet gave me nothing to work on except for the fact that it seems network related.

So I started looking into what can block the messenger. I have three options:

• The PC it self. As this was a problem on more than one PC I did not believe that the problem was here.
• The local firewall.
• My ISP.

My router is a Fortigate box running a relatively new FortiOS 3.0 image. I went in to the protection profile for my outgoing traffic and found that the profile protects me from MSN traffic.

I am not sure why this happens but it was "solved" by deactivating the Messenger scan from within the Fortigate.