its a common one this, The motors have current sensors on them this is what makes them stop when you wind them up or down on auto, unfortunatly when the rubbers get dry and a little sticky these sensors cut in and cut out the motors, the best thing to do is give the motors a hand to wind the windows down and give the inside of the rubbers a realy good dose of silicone based spray,( do not use greese or oil as this damages the seal) then send them up and down a few times then give them another spray and you should find all is well again ;)