All windows? Or only front or rear? I cannot believe that all window gears are suddenly broken.
Did you check all fuses related to this, also under the rear seat? That is controlled by the GM under rear seat = ZKE = central chassis electronics.
The GM has an internal protection system for overload.
Window lifter and SHD=electric sunroof: There are priorities as shown in the technical training manual of the ZKE=central chassis electronics. The relay switches off when
- longer than 60 seconds 36A are recorded
-or if longer than 0,3 seconds there is between 36 and 60A recorded
-or (overloading) - if longer than 0,1 seconds more than 60A flows (short-circuit)
In order to protect the load current circles TSH/ZV/ZS/FH/SHD safely against overload, additionally to the 30A protection an electronic (reversible) current protection is installed in the GM and that is based on the voltage drop on the RM, and depending upon voltage drop (current threshold) the safety relay interrupts the load current. The switching off values of the 30A protection are not reached thereby (these became only then to melt, if a defect at the electronic protection is present). The response threshold of this electronic protection is in such a way put that always before overload of the attached controls one switches off automatically. Automatic restarting takes place after 60 seconds!!!!
However then only if these consumers were switched off and/or no short-circuit is present. Automatic restarting can take place 6 x with switched on Kl./terminal 15. This barrier waived by switching the Kl off. 15. In order not to reach the minimum trigger level when simultaneous switching on of several power consumers, only 2 can be used simultaneously ith the FH/electric window switches. If several buttons are operated at the same time, then only the two first switched ones are implemented. If the overload limit should be already exceeded with 2 switched on FH/window switches, then one FH/window switch is switched off. The FH/window switches for front doors have priority.
Here is the ZKE, unfortunately I only have it it German, but the drawings will help
http://www.e32-schrauber.de/bmw/s-zke.htm
function diagram FH = Fensterheber function diagram FH = Fensterheber = window lifter
http://www.e32-schrauber.de/bmw/daten/zke/bild16.jpg
http://www.e32-schrauber.de/bmw/daten/zke/bild11.jpg
there is also a window limit switch, that is described here
retype it and then use google translate
http://www.e32-schrauber.de/bmw/daten/zke/bild13.jpg