That ISO that you burned, if you open it with 7-Zip/WinRAR/etc, what's in it? I'm asking because in ImgBurn what goes in is what comes out, so something is wrong there.
There's newer firmware available for your burner (remove any disc and close the tray before updating then reboot after it's finished). Also you should get better burns if you used Verbatim DVD+RW blanks