Internet radio on Buffalo Linktheater

Afternoon all,

Just got one of these, and I can't get it to play radio stations.

I can access the web on the unit (which proves there is connectivity)
and can view and play all my media files but when I go to internet >
radio it waits about 10 seconds and then reports "cannot connect to
internet".

The server software is running on my PC. I am on plusnet broadband
behind a NAT router and firewall. Maybe some ports need opening?
--
Regards
Jon