Your game ping is good so I don't think thats the issue here. We're only a small company so we can't do telephone support unfortunately, however you can call Netgear support if you prefer to chat to someone. Go here to login http://support.netgear.com/and you'll be given a number to call - available 24/7.
You mentioned Sky TV and that downloading from it is normal behaviour, this could be the cause as the XR500 cannot control it. Are there any other devices connected to the Sky hub rather than the XR500?