(1) Windex (2) Solution of water/vinegar/soap (3) Solution of hot water and vinegar (4) Mineral Spirits (5) Goof-Off (6) Window Razor Blade (good at removing the bird poop, didn't do a thing to the film)
It's definitely a film on the window -- I can feel it on the outside as a sort of sticky, filmy stuff (although it's lost a bit of the "sticky"). And it's not on every inch of the window; there are places where it's thicker, and little holes in it where you can see straight through.
Does anyone have any other cleaning advice? If I have to, I'll get new panes, but I'm 40' off the ground, so that might be really expensive.