Sound in Messenger

[badamek]

When I use Messenger I can use Video and Keyboard, but I can not use sound. The System tells me that a firewall prevents me. I have shutdown all Virus and Firewall checking, but still the same message regarding Firewall comes. I am using ADSL with a Router. Interesting is that with other programs such as Skype I can Talk.
Any ideas.

Tia

B. A. :)