Hi Patrice58,
thanks for your question! Unfortunately Google changed an API and for proper AppLocking functionality we are requesting on some android versions usage permission. It’s explained in pop-up which is diplayed when you open Mobile Security dashboard for first time. We don’t misuse this sensitive permission for anything else.
Could you please more describe your problem, steps to reproduce including your android version and device? Or it would be the best if you can create new ticket to our support guys http://support.avast.com/. And then post a ticket number here - I will try to help as much as I can.
Thanks,
T.