one addition to my previous post.
the first time it happened I haven't immunized yet. Afterwards I triedd to immunize and undo immunize but nothing happened. At any time any url/domain appears in the black list: the list is always empty.
At a certain time spybot refuses to connect even the google url. I had to restart the PC to enable google again.
I think there is something blocking port :80
many thanks for the help