Hello Giacomo!
Sorry for not giving my details, but I thought only Windows 8.x users have these kind of problems.
I am using Windows 8.1 on a Lenovo Thinkpad E540.
As for the suggested new driver versions - I have already installed that version - just before I worked out the Task Scheduler solution, but unfortunately the WIFI connection failed right after the next resuming. Maybe the drivers are really sensitive about the WIFI router one tries to use.
Your solution clearly the recommended way to solve the problem, but if that doesn't not work (like for me) for some reasons, there is my workaround.
Best regards, Kalman