Try disabling all hardware and software firewalls (temporarily of course) and see if that works. Then turn on the software firewall and see if it still works. If yes, then check out your router settings. If no, check the software firewall settings.
Also, if your router is set up as a DHCP server, this might prove aggrevating when forwarding ports to the streaming computer. The streaming computer's IP address MAY change periodically and will nullify the settings in the port fowarding section of your router because the IP addresses do not match now. Check you streaming computer's IP address by opening up command prompt (in Accessories) and then typing in IPCONFIG and hit enter. Make sure this IP address matches what you have in the Port Forwarding section of your router.
Either a firewall is blocking those ports or the router is not properly configured to foward the proper ports to the proper computer. You probably already knew this, but I am just suggesting that whenever you troubleshoot, do so methodically.