Try with other "theme styles". There must be some css property to control which item is sent to the front and which to the background... If you find it working as you expected in some other theme, then you can use the "web developer toolbar" for Firefox to let you show the css properties, change them to see if that makes any difference, until you find the right values.
Additionally, you could file a bug report about it (specially if you can't find a solution):
P.S: I don't use this popup, sorry I can't tell whether it works for me or not. I know it's know to work for other people, so ther must be a small bug related to display.