I'm also having this problem and it's a big one - my client is really annoyed that they paid for Juicebox Pro and can't have multiple expanding galleries on a page. It's a showstopper, so I'll now need to invest a huge number of hours replacing Juicebox on their site with a gallery that actually works as advertised. I checked the Twitter page but couldn't see any update on this issue.

I also notice that expanding the gallery and then closing or un-expanding it reloads my page without scrollbars so the user can only view the top content on the page! This happens on Chrome & FF so far. This doesn't happen on the demo page so I'll continue to look for the problem.

These are major problems with the gallery. If they can't be fixed I'll be seeking a refund for my client (the features page clearly states you can embed multiple galleries in a page - what point if they can't be expanded?)