tagcloud not working

I am using the shortcode [tagcloud] on a page. The tagcloud is shown and when I click a tag, the images with this tag are shown as a list. But when I click an image, I just get back to the tagcloud. I expected to view the image large as with another gallery. When I click the same tag again, I get unknown page error. I deactivated all other plugins and switched to the TwentyTwelve theme with no effect. See the page here.

https://www.ads-software.com/extend/plugins/nextgen-gallery/

[No bumping, thank you.]