Just noticed this today when I was driving around town. If you are wearing polarized sunglasses and look at a car windshield which has the metalic film between the layers that many people have said kills detection range, it apears very bright orangish color almost like well coated optics on rifle scopes or rangefinders would look, but even more so (so much to where I could barely even see through the glass mith my specs. on). I pulled my glasses off to see if it was apparent without them and the glass looked like normal old glass. The types of cars I noticed this on were a lot of GM cars like high end buicks. If I remember right Mike V mentions many of these cars have unnacceptable windsheilds.
That being said, if you have been getting real bad range, buy or borrow a pair of polarized specs and take a look in sunlight at the glass, you might be suprised at what you find. I also noticed the glasses had the same effect on metallic versus just plain tinted windows. Im pretty sure it is because polarization of the lenses takes the glare off of the surface of the glass (reason they are popular with trout fiisherman, makes the water more transparent) thus allowing you to see direct sunlight reflected off the metallic layer, just a thought though.