I had the same problem and I fixed it. For me, it was because I am on the Rogers network in Canada. Regardless of where you are many cellular neworks use firewalls and something called NAT (Network Address Translation). Nokia should really make people aware of this because probably 50% of people around the world have this problem. The solution for me was to use Rogers VPN or Public IP to access the internet. Rogers blocks access to this internet connection so you have to add the service to your account for $10 per month but I have heard that other carriers like FIDO have not blocked access to it.
On the Nokia n79 this requires creating a new access point under TOOLS>SETTINGS>CONNECTIONS>DESTINATIONS. Add a new access point with the following settings:
Connection Name: Rogers VPN (or whatever you want to call it)
Data Bearer: Packet Data
Access Point Name: vpn.com
User Name: wapuser1
Prompt Password: No
Use Access Point: After Confirmation (or change if you want something else)
That's it. When you load the internet radio Application and it lists your options select "Rogers VPN". If you don't see it in the list, press the soft button for Options then "Select Access Point" and you will see the full list. If you want the VPN to be the first thing you see you can change the priority under destination settings. Just select the VPN and press "Organize" then "Change priority".