Thanks for your response.

Can you explain exactly what do you mean by "shutting off media sharing on the computer"? Do you mean on the PS3? I have tried disabling the Settings > Network Settings > Media Server Connection, if that is what you mean.

On my PS3 my primary DNS server is my router, and my router has primary and secondary DNS servers automatically setup by my CSP (Orange) with what appear to be reasonable values (e.g. 193.36.79.101 [cache1.orange.net]). I am not sure if DNS can be the problem as, from my PC (which uses the same router), if I try to "ping eu.playstation.com" or "ping en.playstation.com" it resolves the DNS names to IP addresses successfully (e.g. eu.playstation.com returns 217.18.19.155). There is no response to the ping, but that could be the way that the eu.playstation.com servers are configured, as us.playstation.com refuses pings whilst I can browse to the corresponding website.

Hmmm...