I had the same type of thing on my 08 windshield....looked like an overspray of something and just wouldn't come clean. Finally I bought a bug sponge and some Pro Goof Off. I applied a small amount on the sponge and spread on the affected area. I let it sit for about 15 seconds and then I took a straight, one edge utility blade and went over the area. WOW, it came off with ease! I of course then proceeded to apply more "goof off" and cleaned the entire area. Again, I suggest you spray onto the sponge and not directly to keep from getting all over other things. Hope this works for you....let me know.