Why are you gluing this down? This is designed to be a floating floor. Here is the installation guide. I skimmed it briefly, not having worked with this particular product before, but I saw no mention of gluing it down. I'll look at the guide more closely when I have the time.
http://www.armstrong.com/content2/resam/files/24785.pdf
http://www.armstrong.com/content2/resam/files/24785.pdf