The rear windows of my Forester creak quite loudly when they are closed, which is rather annoying. If I open them about 5-10mm, the noise stops. I thought that lubricating the window channels with WD40 might help but it doesn't. Has anyone else had this problem? Can anyone suggest what I can do to stop the creaking? Any help will be much appreciated. Thanks, Keith.

WD40 is not a lubricant. WD stands for "water displacemen" formula 40.

Try silicone spray. 

Thank you. I will try that.