bbftx,
Well, I've tried to install and configure a Hoverbox gallery, and I also encountered problems - though slightly different then you. Installing the package copied the directories into my project, and put "Hoverbox" along with the two examples in the Plugins drop-down list. However, clicking on either of the examples produced no effect at all. When I examined the example's code, I found that the path to the example images was incorrect. But, even when I fixed the path, the examples still did nothing when selected from the drop-down list.
When I examined the examples further, and this is what I discovered: Hoverbox is an inage display technique that employs CSS. That CSS file is setup to require a gallery to be in an unordered list with the classname of "hoverbox", and each list item to be contained in a link. Each list item must have two image tags that have their src attribute set to the same image. The second image tag must have a classname of "preview".
Hope it helps,
jvcbiggles