Hey. Possibly a silly question but I have a rubber tipped stylus for notes and sketches that I use with my iPad 2. It was great when. Got it but not it is not very good. I need to apply a bit of pressure for the iPad to detect it and by that point it's got too much friction on the screen and doesn't slide smoothly, making writing impossible. Weird thing is it works perfect with my iPhone 4. Could this be dirt in the iPad screen? I have cleaned it with a microfiber cloth but no change. Help?