Thank you for the additional information.
I have now been able to replicate the problem. It seems to happen in IE8 and IE9 when imageTransitionType="SLIDE" (the default value for this configuration option).
I have logged a bug report with the developers and it should hopefully be fixed in the next version of Juicebox.
In the meantime, it looks like a suitable workaround would be to set imageTransitionType to something other than SLIDE (FADE, CROSS_FADE or NONE).

If you require an invoice for your purchase (as a PDF document), then please fill in this Juicebox-Pro Invoice Request Form.
Thank you.

In Touch Input Mode (on mobile devices), a tap on the screen (anywhere other than on a button) will toggle the overlay on and off. (Images can still be navigated by swiping left and right.) It sounds like this might be what is happening.
Try setting showInfoButton="TRUE" (in JuiceboxBuilder-Pro's 'Customize -> Button Bar' section). This overrides the default behavior for the overlay and it will be toggled on and off only when the user clicks on the Info Button on the Button Bar.

What you are referring to is likely to be the SEO Content produced by JuiceboxBuilder-Pro. It is selected by default but you can switch it off by deselecting the 'Add SEO Content' checkbox in the 'Customize -> Sharing' section.
This code is used purely for Search Engine Optimization reasons and is not actually required for the gallery itself at all. Please see the SEO support section for further details.

@jtmpusr

Thank you for your suggestions.
Here are some notes on a few of your topics.

With Juicebox-Pro, you can have multiple rows of thumbnails by increasing maxThumbRows from its default value of 1.
For reference, a list of all available thumbnail configuration options can be found here.

You could source your gallery using a Flickr account and tag your images in Flickr.
Each link in your web page could use JavaScript to set the Juicebox configuration option flickrTags in the gallery's embedding code accordingly and then reload the gallery using the selected tag or tags.

JuiceboxBuilder-Pro (which comes with Juicebox-Pro) has a number of preconfigured gallery layouts known as presets which you can choose from. Many of the presets available will allow you to instantly configure your gallery to look like the demo galleries on this web page. For more information about presets, please see the JuiceboxBuilder User Guide.

I have not been able to replicate this behavior in any test galleries of my own in IE11 (or in IE9 Document Mode within IE11).

Also, do you see the problem in any of our own demo galleries on this web page or just in your own gallery?

There might be an element on your web page which is partially obscuring the thumbnails (which, for whatever reason, is only a problem in Internet Explorer). You should be able to see if this is the case using a browser's developer tools (usually F12).

It might also be wise to check your web page for HTML errors using the W3C Markup Validation Service.
If there are errors on your web page, it might be worth trying a different WordPress theme to see if this makes a difference.

It might also help to ensure that your version of Juicebox-Pro is up-to-date.
Juicebox-Pro v1.4.1 has just been released so please try upgrading your WP-Juicebox plugin to Juicebox-Pro v1.4.1.
Instructions on how to get download the latest version can be found on the Upgrading Juicebox support page and instructions on how to upgrade WP-Juicebox can be found here.

This bug has now been fixed in v1.4.1. Please see the Upgrading Juicebox support page for details.

This bug has now been fixed in v1.4.1. Please see the Upgrading Juicebox support page for details.

In order to upgrade JuiceboxBuilder-Pro, it is necessary to first uninstall any existing version.
Please try the tips in the Installation Issues section of the JuiceboxBuilder User Guide.
Hopefully this will help.

Implementing the above (to have a lightbox open to display an image when it is clicked) into galleries created by WP-Juicebox can be done but would require quite a bit of work as the plugin does not have any built-in lightbox-style functionality, does not have interface support for linkURL or linkTarget and the embedding code that the plugin provides would have to be modified to include the custom JavaScript code required.

(1) Install and activate WP-Juicebox.
(2) Upgrade WP-Juicebox to Juicebox-Pro following the instructions here (required for setting imageClickMode="OPEN_URL" and for using the Juicebox-Pro API).
(3) Install and activate the Shadowbox JS plugin (and download the Shadowbox source files from within the plugin's settings page).
(4) Open the 'wp-juicebox/config.php' file in a plain text editor and change all three instances (on lines 47, 74 and 98) of:

$image_element->setAttribute('linkURL', $image_url);

... to:

$image_element->setAttribute('linkURL', 'javascript: func();');

(5) Also, in the same file, change all three instances (on lines 48, 75 and 99) of:

$image_element->setAttribute('linkTarget', '_blank');

... to:

$image_element->setAttribute('linkTarget', '_self');

(6) Open the 'wp-juicebox/wp-juicebox.php' file in a plain text editor and change lines 240-251 (the $string_builder section) to the following:

$string_builder = '<!--START JUICEBOX EMBED-->' . PHP_EOL;
$string_builder .= '<script type="text/javascript">' . PHP_EOL;
$string_builder .= '    var jb;' . PHP_EOL;
$string_builder .= '    jQuery(document).ready(function () {' . PHP_EOL;
$string_builder .= '        jb = new juicebox({' . PHP_EOL;
$string_builder .= '            backgroundColor: "' . $background_color . '",' . PHP_EOL;
$string_builder .= '            configUrl: "' . $config_url . '",' . PHP_EOL;
$string_builder .= '            containerId: "juicebox-container-' . $gallery_id . '",' . PHP_EOL;
$string_builder .= '            galleryHeight: "' . $gallery_height . '",' . PHP_EOL;
$string_builder .= '            galleryWidth: "' . $gallery_width . '"' . PHP_EOL;
$string_builder .= '        });' . PHP_EOL;
$string_builder .= '    });' . PHP_EOL;
$string_builder .= '    function func() {' . PHP_EOL;
$string_builder .= '        var index = jb.getImageIndex();' . PHP_EOL;
$string_builder .= '        var info = jb.getImageInfo(index);' . PHP_EOL;
$string_builder .= '        var url = info.imageURL;' . PHP_EOL;
$string_builder .= '        var title = info.title;' . PHP_EOL;
$string_builder .= '        Shadowbox.open({' . PHP_EOL;
$string_builder .= '            content: url,' . PHP_EOL;
$string_builder .= '            player: "img",' . PHP_EOL;
$string_builder .= '            title: title' . PHP_EOL;
$string_builder .= '        });' . PHP_EOL;
$string_builder .= '    }' . PHP_EOL;
$string_builder .= '</script>' . PHP_EOL;
$string_builder .= '<div id="juicebox-container-' . $gallery_id . '"></div>' . PHP_EOL;
$string_builder .= '<!--END JUICEBOX EMBED-->' . PHP_EOL;

(7) Enter imageClickMode="OPEN_URL" in the Pro Options text area of your gallery's settings window.

Please note that the procedure above has not been tested extensively and I cannot vouch for the robustness of the solution or the stability of WP-Juicebox itself after making these modifications.
However, I hope it help and at least points you in the right direction.

[The line numbers above refer to the current version of WP-Juicebox (v1.4.0.1).]

When using a Picasa Web Album as the source of image, WP-Juicebox uses the Picasa image 'title' as the Juicebox image title (which by default is the image filename) and the Picasa image 'summary' as the Juicebox image caption.

If you want to prevent WP-Juicebox from displaying the Picasa image 'title', please do the following.
(1) Open the 'wp-juicebox/config.php' file in a plain text editor.
(2) Change line 101 from:

$title_text = $dom_doc->createCDATASection($attachment->title);

... to:

$title_text = $dom_doc->createCDATASection('');

Please note that the line number above refers to the current version of WP-Juicebox (v1.4.0.1).

On a single monitor, when useFullScreenExpand="TRUE", it is not possible to move the cursor outside an expanded gallery so that the overlay fades out.
One possible alternative would be to set showInfoButton="TRUE" (in JuiceboxBuilder-Pro's 'Customize -> Button Bar' section) and you can then toggle the overlay on and off using the Info Button on the Button Bar. The Button Bar will be displayed on screen all the time (allowing access to the Info Button) but all other components on the overlay (for example the caption area and the main image navigation buttons) will be toggled on and off.

The XML file used for the http://sandbox.castarchitecture.com/pro … homes.html gallery is not the one you quoted.
The gallery uses this XML file which does not set the two configuration options from my post above: http://sandbox.castarchitecture.com/pro … config.xml

If you want your gallery to use the http://sandbox.castarchitecture.com/TEM … config.xml file, then you can point towards it in your gallery's embedding code using a configURL configuration option or, alternatively, as your 'TEMP_JUICEBOX_FOLDER' folder seems to be a complete gallery folder, you can use a baseUrl, for example:

<!--START JUICEBOX EMBED-->
<script src="/TEMP_JUICEBOX_FOLDER/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        baseUrl: '/TEMP_JUICEBOX_FOLDER/jbcore/classic/theme.css',
        containerId: 'juicebox-container',
        galleryWidth: '100%',
        galleryHeight: '100%',
        backgroundColor: 'rgba(255,255,255,1)'
    });
</script>
<div id="juicebox-container">
</div>
<!--END JUICEBOX EMBED-->

If you do not specify either a configUrl or a baseUrl, Juicebox will look for a file named 'config.xml' in the same directory as the page containing the embedding code. In your case, there is such an XML file in that location but it is not the XML you want your gallery to use.
(Alternatively, you could replace the http://sandbox.castarchitecture.com/pro … /config.xm file with http://sandbox.castarchitecture.com/TEM … config.xml on your web server.)