Just in case someone meets a similar problem:
Turning off the power of the computer, as mentioned in French in the post number 5 of the following link, gave me again access to the mouse and an easy reboot of the computer.
https://www.alionet.org/showthread.p...ight=enumerate
I will check if this silly solution works again next time I download a book from Caliber on my Kindle.
Thanks again,
Jeanphi