Does it only do it when it is dry? i.e does it do it when the window is wet? My spider squeaked on being raised and it was due to the glass on the rubbers. It didn't do it when the rubbers/window were wet.
Both my front windows did this until a liberal application of silicone grease from an aerosol sent them both silent again. I went a bit mad with the driver's side and was still seeing it on the window weeks later so try not to do that!