Well I took a peek at the colorbox.css file, but couldn’t determine what was was amiss, so I found a friend with a lot more experience and he soon spotted that the command #cboxSlideshow.hover should be #cboxSlideshow:hover. He also changed ‘the offset for the Running-Hover rule’ (but I’m not sure what that means!!). Anyway the slideshow control icons behave as expected now on my website and I’m happy.
This is a really great plug-in in my opinion, especially for a membership site. It is fairly straightforward for users, if they are familiar with creating and publishing a blog post, to create a gallery using the WP Add Media tool. This plug-in adds a tremendous way to display the photos in any post or page gallery.