I'm glad to inform you that after uploading 2.2.8.0 (except the ClientScript and Data folders as mentioned in your blog) and doing a clean install, the layout issue has been solved. And strangely enough, I don't even have to move the skin files to App_Themes\default. (Anyhow if I move the files there, the layout problem occur again)

And yes, the app pool is already set to classic all the while.

But with this installation, I've came across several issues while doing the installation. I will post them at the Installation forum.

Thank you very much for your support and help.