I have two areas that look like rings from a glass or from a can of something that I just can not get off. Started with Windex, then Goo-Gone, then Goof-Off, then Oops, then a razor blade and they are still there. Other than just giving up and buying a new sheet, does anyone have any ideas? I just can't believe they are still there. Its like they are etched in the glass or something but it looks exactly like a glass ring as is has even ran from the original ring. I thought maybe it was from a can of acrylic or something but I sure would have thought that a razor would get that off. I am stumped.