Thanks Konstantine, but that didn't help either.
However, I found a quick&dirty solution:
1. I temporarily removed all <A HREF ...> and <A NAME ...> tags from the file.
2. Replaced the original file with the adapted version.
3. Spidered the adapted version, which went great !!
4. Replaced the updated file with the original one.
It does work for me but, although the files on my site will change only every few weeks, I'm not looking forward to do this trick every time
So if anyone has an idea for a clean solution ....
Peter