Steve,
I may have misunderstood what you're seeing at the bottom of the page, but did you set a 'start group on next page if less than' value in your group footer that could be causing this?

>There are several lines in the detail band. Each has several fields. At run time, all of the fields on any given line evaluate to blank. A blank line still prints, causing the detail band to create a large gap. (But this only seems to be happening at the bottom of the page)