Are you sure it's the windscreen, and not the wipers? I recently looked into replacing my wiper blades with a set of "silicone" blades, thinking they would have better "slip" over the screen. I was told that in fact silicone blades are a poor choice over normal rubber ones as the silicone "grips" as it moves over the screen, giving that aggravating noise like someone running a fingernail down a blackboard.
You did say that you replaced your blades recently, but did you replace silicone with silicone? IF you arent sure (or cant remember) if they were silicone ones you fitted then a $10 a set of rubber replacement blades might be a good investment.
Regards,
Leon
Started out with nothing Still got most of it left