AppleTV (2) and Cisco SRP527W modem/router not playing nice

Hi,

I have a home network with a brand-new apple TV (April 2012). Everything works ok using my Billion 7800N modem/route on wireless. (Ethernet connection is not possible).

However, I have a (also brand new) Cisco SRP527W modem/router which I would prefer to use (slightly better speed, more stable on my dodgy telephone line).

Problem is, when I use that modem/router, everything works except ATV. The modem has the latest firmware, but is rated as a business modem, and It seems that some reconfiguration (of port numbers, I suspect) is required to make this work.

Does anyone know how to set up the Cisco SRP527W to work with Apple TV?

Any help gratefully appreciated...

Thanks,

:)

Mike