Please see the Juicebox - Version History for a full list of changes between versions.
If you use, for example, Juicebox-Pro v1.1.1, you would not be able to use the thumbsPosition 'LEFT' and 'RIGHT' options which were introduced in Juicebox-Pro v1.2.0.
Also, there are usually several bugfixes between versions so I would recommend keeping your version of Juicebox-Pro up-to-date.

This seems to be default Lightroom behavior.
It happens when going to the 'Web' section and selecting any 'Layout Style' (even Lightroom's own 'Lightroom Flash Gallery' or 'Lightroom HTML Gallery').
The gallery will consist of all images in the chosen folder (or collection), not just the selected ones.
The solution is to group all the images you require for a gallery together into a separate folder (or collection) prior to creating the gallery.

In replacing the 'jbcore' folder in a gallery, you are converting the gallery to the version of Juicebox whose package the 'jbcore' folder came from.
The 'jbcore' fodler is the core Juicebox (non-image) part of the gallery.
When you upgrade Juicebox, the 'jbcore/classic/theme.css' file may change, in which case you would need to incorporate any customizations into the new file (rather than just replace it with your old one).

With regard to your query about removing the drop-shadow from the Gallery Title, as I mentioned, the line number I quoted refers to the 'jbcore/classic/theme.css' file from Juicebox-Pro v1.2.0.
It sounds like you wish to remove all drop-shadows from the gallery, in which case just open the 'jbcore/classic/theme.css' file in a plain text editor, search the file for all instances of 'shadow' and remove all the lines which contain this search term.

You can replace the navigation buttons by editing the 'jbcore/classic/img/assets.png' file in an image manipulation program such as Adobe Photoshop. Please see the Juicebox -Theming page for more details.

Unfortunately, the forum attracts a lot of spam.
If a spam entry is posted in a thread that you are subscribed to, you will automatically get an email notifying you of a new post in that thread as soon as the post is entered.
However, I am pretty quick off the mark in spotting and deleting spam and the links you are emailed refer to these spam posts which no longer exist.
We have anti-spam measures in place on the forum but, inevitably, some spam always seems to get through.

If you added the images using the 'Add Media' button whilst creating a new post, the images are automatically attached to that particular post.

If you add images to the Media Library by clicking the 'Add New' button on the Media Library settings page, then you will have the option to attach each image to a post by clicking on the word 'Attach' in the 'Attached to' column on the Media Library settings page.

You could use imageScaleMode="FILL" to completely fill the image area with the main image (though cropping may occur on large images). However, the thumbnails are of fixed dimensions and are centered within the gallery and the gallery is embedded in a container with a fixed width on your WordPress page. If the container was slightly narrower that it currently is, there would be less room to the left and right of the thumbnails but the container size is set by your WordPress theme. You could check your WordPress theme settings to see if you could decrease the post container width.

Since you have set thumbNavPosition="BOTTOM", Juicebox is reserving space for the thumbnail navigation buttons below the thumbnails.
If the gallery was embedded in a container which did not have a fixed width and the user decreased the width of the browser window, the number of thumbnails per page would decrease and the thumbnail navigation buttons would appear in this space to allow the user to navigate through the thumbnail pages.
If you find a way to change your post container's width in your WordPress theme settings, you might like to try increasing the post container's width slightly and reverting to setting thumbNavPosition="CENTER".

@rocksta669

Make sure that you are using the latest version of WP-Juicebox (v1.2.0) and check that the numeric NextGEN Gallery Id (taken from the 'Dashboard -> Gallery -> Manage Gallery' page) matches the 'NextGEN Gallery Id' that you enter into the Juicebox settings window.
If using WP-Juicebox v1.1.1, after creating your NextGEN Gallery, you will need to 'Edit' the post containing the gallery and 'Update' the post or go to the 'WP-Juicebox -> Manage Galleries' page and 'Edit' the gallery itself and click 'Save' (without changing anything) in order to rebuild the gallery's XML file with the new image data.
(It is not necessary to do this in the latest version of WP-Juicebox v1.2.0, though you may need to clear your browser's cache before reloading the gallery.)
If you continue to experience difficulties, please post the URL to your web page so that I can take a look.

Use a background color with an opacity value (the 4th rgba parameter) to 0.
If using JuiceboxBuilder-Lite to create or edit your gallery, just set the 'Background Color Opacity' to 0 in the 'Customize' section.
Your embedding code will look something like this:

<!--START JUICEBOX EMBED-->
<script src="jbcore/juicebox.js"></script>
<script>
new juicebox({
containerId : "juicebox-container",
galleryWidth: "100%",
galleryHeight: "100%",
backgroundColor: "rgba(34,34,34,0)"
});
</script>
<div id="juicebox-container"></div>
<!--END JUICEBOX EMBED-->

First of all, please check that your web server meets all the requirements for WP-Juicebox v1.2.0 and make sure that you are logged in as an Administrator.

Try adding a gallery by either:
(1) clicking the 'Add Juicebox Gallery' text button (in 'HTML' mode), or...
(2) clicking the Juicebox icon button (in 'Visual' mode)
Do you get the same error message when trying both of the above methods?

Another user recently experienced a similar problem when using the BulletProof Security plugin.
If you use this plugin, please see this forum thread: http://juicebox.net/forum/viewtopic.php?id=369
You may need to add the following code to your root .htaccess file in order to configure BulletProof Security to work with WP-Juicebox.

# Juicebox skip/bypass rule
RewriteCond %{REQUEST_URI} ^/blog/wp-content/plugins/wp-juicebox/ [NC]
RewriteRule . - [S=13]

If you do not use the BulletProof Security plugin, then there may be a conflict with a different plugin.
Try temporarily deactivating all your plugins and reactive them one-by-one (checking to see if you can successfully add a Juicebox gallery after reactivating each one) until you find the conflict.

The versions of SimpleViewer used by the two plugins differ greatly in format.
'Airtight SimpleViewer' uses SimpleViewer v1.8.5 whereas 'TTG SimpleViewer' uses SimpleViewer v2.3.0.
SimpleViewer was re-written from the ground-up for v2.
SimpleViewer v1.8.5 embeds a single SWF file in a web page whereas SimpleViewer v2.3.0 uses a collection of CSS, HTML JavaScript, SWF and image files (in the 'svcore' folder) in order to support Universal Playback.
Also, the tag and attribute names within the gallery XML files changed between v1 and v2.

In order to convert a SimpleViewer v1.8.5 gallery to a Juicebox v1.2.0 gallery, you will first have to upgrade the SimpleViewer gallery to the current format by opening it in svBuilder and re-saving it on the application's 'Publish' tab.
You should then be able to convert the gallery to a Juicebox gallery using JuiceboxBuilder.