Please post the URL to your gallery so that I can take a look at it.
It would be much easier to troubleshoot your problem if I can see it for myself. Thank you.
In the meantime, please make sure that you are using the latest versions of Juicebox and Showkase.
Upgrading Juicebox: http://www.juicebox.net/support/upgrade/
Upgrading Showkase: http://www.showkase.net/support/upgrade/
The default captionPosition (used by Juicebox-Lite) was changed from OVERLAY to OVERLAY_IMAGE in Juicebox v1.4.3 and the Lite Full demo gallery you quoted uses captionPosition="OVERLAY_IMAGE".
If you are using an older version of Juicebox, your gallery will be using captionPosition="OVERLAY" (and captionPosition is a Pro option which cannot be changed in Juicebox-Lite).
This may explain your problem, in which case upgrading your Juicebox gallery (following the instructions in the link above) will solve it.