Did you skip a step? Where is the creation of the dome step? Clicking on either one of the three icons on the left side of the taskbar, in this case, the full globe is preferable. You can also hide the ground through the utility tab of EZDome. I was unable to duplicate any problems through my install. However, I noticed in the creation of the preset panel that the inner dome has an HDRI associated with it. If I am correct, it's the outer dome that provides illumination to the scene and the inner dome just the dome background, which can just be a plain jpg image. At least, that is what I get when I use sIBL. But if you don't have a dome in place, the preview background will show up white.