Heard loud bang and now the front driver side door window does not roll up. I can hear the motor working, but the window still does not roll up. One week later the exact same thing happened to the front passenger side window. What could it be and how much is it to fix?

Possible that the mechanism has jumped off the linkage . You will need to remove the flap and get access to the window winding mechanism. You will be able to notice the main motor mechanism which has either jumped off - as you heard the sound- or there is a gear that has come off the motor drive.
A resetting of the winder to keep the motor drive coupled to the window winding mechanism should solve. Also make sure that the glass channels are clear and free , not giving friction to the mechanism to jump off.