I have attempted to install the Facebook Page Promoter Lightbox and it doesn't work. It's not an issue of it 'loading' per say, it simply doesn't show up at all when it's installed. I tried the install through the WordPress dashboard. Then I deleted the plugin and attempted to install it by adding the folder through FTP in the corresponding plugins folder.
I even tried to add the code straight into the blog with "Appearance -> Editor" by taking the code from a source of another site that uses it and inserting in the appropriate Facebook ID etc.
The blog I work with is http://www.glossandglam.com/blog . I can't see much that it would conflict with on the page. If you check out the source code, as you can see the plugin doesn't show up on the site even though it's been installed and set up through the WordPress framework.