Are there any hidden firewalls?
Until yesterday everything worked just fine: no brickwall.
Sometimes , for some reason, the brickwall reappeared; so with Windows XP I used to restore the system to the previous day and everything worked normally again. What made that brickwall reappear I don't know.

Still yesterday that solution didn't work.

I disabled all my firewalls: windows firewall, my Trend Micro PCillin firewall, my router (Orange livebox firewall) so puzzled I was, but nothing doing LW was still behind a firewall!! So, what firewall could it be?

Because I need protection I turned on my antivirus firewall again, also my router's which is configured to allow LW anyway.

For months on end everything worked perfectly and suddenly, somewhere a firewall is running and I can't turn it off.

Don't use 2 software firewalls. They have a tendency to clash with each other and result in unreliable results & less security. So choose one or the other. In your case, either XP or PCillon firewall. Disable the other. And make sure you configure the one you use to allow LW full access.

Most routers have internal NAT firewalls. Some have UPnP which allows a UPnP capable program like LW to communicate with the device to open a port when it is open. However, different brands of routers use different UPnP technology, and some UPnP implementations are not reliable. It's my guess that this is your problem. It may take some time for the UPnP to be triggered or else, it is simply unreliable. The best answer in that case is to forward a port in the router.

Their website was not very helpful. After a search, it seems other people have had problems with that device. See Forums - Can't connect to my Orange Livebox - PC Advisor; ie: the firewall not turning off.