Maybe your problem does lie with the electronics as the others have said. My 300E isn't so complex. However, I've found that the rear windows on my car often will not open after a long period of not opening them. It seems that the windows stick to the seals. I gently tap around the inside and outside edges of the windows using the heel of my hand. After doing this once or twice, the windows will open. I'd bet that this is why the PO kept having the window switches replaced unnecessarily. It helps to have the engine running so the higher voltage gives a little boost to the window motors.

It is a good idea to "exercise" each window at least once a week to prevent the sticking.

__________________
1986 300E
1993 Volvo 940 Wagon
1984 Volvo 240 (daughter's)
1976 Dodge 1/2T pickup, gas hog