I have the same problem. Let me pass on what I've learned so far from reading previous threads.
You must install the latest version of Flash Player (10,2,152,26) http://www.adobe.com/software/flash/about/
The problem could be blocked router ports; Port 1935 must be open;
To get the address go to Start > Run. Then type in cmd hit enter, then in black box that appears type ipconfig. Then copy the IP address listed under Default Gateway and type it into an internet browser - it should be something like - http://192.168.1.254
If it asks you to login, try the username admin and a blank password as they're usually the default details. If that doesn't work you'll need to speak to your ISP or check the documentation that came with you router.
Once you're logged in look around for the Firewall settings and there should be an option to open ports there.