I've got the nasty suspicion that the previous owner of my CRX coated the inside of all windows with these nasty chemicals. Unfortunately (if it was Fog-X) it doesn't quite work and actually makes clearing the screen a lot harder than necessary, plus it fogs up even more readily.
At first I thought it was some silicon film from all the stuff he used to clean/"beautify" the interior plastic but that normally comes off with the cleaners I use...
Anyway, so far I've used normal (domestic) window cleaner and Halfords cream cleaner (the one you let dry on the screen and then buff). The Halfrauds cleaner normally cuts through pretty much all the crap that ends up on screen but in this case it didn't even dry - it formed small droplets on the coating :(.
Anyway, I *have* to get this crap off as it's seriously affecting my ability to look out of the windows.