Thanks, Stief, for the data, first, I know now at least that the message in the console has nothing to do with LW (true, I've got a canon Lide20). Second, I didn't know that LW was able to change now and then its port nr... it never did it before.
I've tried to come back to the previous version (4.10.9) but after a day where it seemed to work OK, it has started again to be only at good or excellent connection... so it was not the version !... I really wonder !...