Unfortunately, as you have discovered (and as noted in the 'Known Issues' section of the JuiceboxBuilder User Guide), JuiceboxBuilder does not accept images with apostrophes in their filenames.
JuiceboxBuilder will not accept images with the following characters in the filename: #, ? and '. Please rename files before importing to JuiceboxBuilder.
The apostrophe (single quote) is a reserved character and, as far as I am aware, there are no immediate plans to allow JuiceboxBuilder to accept this character.
As an image filename forms part of a URL when uploaded to a web server, it would be wise to use only web-safe characters within image filenames. Please see section 2.3 of this document for details.
Characters that are allowed in a URI but do not have a reserved purpose are called unreserved. These include uppercase and lowercase letters, decimal digits, hyphen, period, underscore, and tilde.
You should have no trouble (either in JuiceboxBuilder-Pro or on your web server) if your image filenames use only these web-safe characters.
With this in mind, I would recommend renaming your images and their corresponding imageURL entries in your gallery XML files.
You can batch rename multiple images very quickly with a third-party tool such as Bulk Rename Utility.
You can also quickly and easily rename all imageURL entries in an XML file (or in multiple XML files) at once with a single global search and replace action in a text editor which accepts multiple files and supports regular expressions such as Notepad++.
I realise that this will add a couple of steps to your workflow but, as JuiceboxBuilder does not accept filenames with apostrophes, renaming your images (and their corresponding imageURL entries) is the only way for JuiceboxBuilder to convert your SimpleViewer galleries (and with the right tools, renaming the files and imageURL entries should not take too long).