judging by the comments on google,.
The homehub firewall permantly stealths all pings and other attempts to get direct responses, usually a useful thing.
However the suggestion Here
at the end of page 1 suggests that the way to resolve it, is to use the DMZ function to send all 'other' traffic to a specific local IP address. This local IP address can then respond to ping.
Ping does not work on port 80, but is an ICMP request, so opening port 80 will have no impact (and if not needed, remove it). NB: DMZ is effectively doing the same for all ports.. .and all types of traffic not otherwise responding to an request that originated on the LAN.
Normally the firewall just dumps that traffic in byte bucket/bin and hence that is why you see no response. Many routers do provide a local response to ICMP/ping and other diagostic commands... the home hub clearly does not.
So as above point (locally) unexpected traffic at something that can respond (even your PC - with its firewall enabled) and it will be fine.