I think this is a Google Chrome specific bug. It seemed to work in Firefox.
Looking through all the options, I found this on the slideshow settings page.
The path to imagerotator.swf is not defined, the slideshow will not work. If you would like to use the JW Image Rotatator, please download the player here and upload it to your Upload folder (Default is wp-content/uploads).
Not sure what it means, I just want the default viewer to work, I never used this “JW Image Rotatator”. At least not knowingly.
It looks like I’m having a related problem. I also don’t have the close button and it seems like your next/previous buttons are doing the same thing mine are. I can load one picture, but if I click next, it gets stuck on “Loading”. Not sure if they’re related, but I think we have the same issue.
I’m using WordPress version 2.8.5 and NextGEN version 1.4.3.
My site is http://tom.swogger.net.
My original post is here – http://wordpress.org/support/topic/332585
Anyone have an ideas?