I manage to overcome the problem by opening one of the existing projects (say
1996) by double-clicking in the corresponding whtt file.  Once in Winhttrack,
i changed the project name to 1998, changed the url list to 1998, and the
program started owrking as it should.  

I wonder if this results from the fact that I use a predetermined set of
rules, which I load with each new project added to the news folder (1996,
1997, 1998, etc).