Mchale, I've had the same problem printing onto transparency paper (not sure exactly what kind): it would not dry. I found a roll of some similar sheet plastic (also not sure what it was) and it worked fairly well; as long as I didn't rub it too hard, the ink would stay.
Lacc, thanks for sharing
I'll try looking that up. 100% clear might not be a problem if the windows are designed to have a little tint to them anyway.