It seems there is a problem with the NextGen Gallery Plugin and the WPML Multilanguage Plugin. Once I activated the WPML and tried to add a new gallery and create a page for it, the page wouldn't show up. Also NextGen creates errors while uploading pictures and the thumbnails can't be generated. If I turn off the WPML all seems to be ok. I can regenerate the thumbnails and the before created page that goes with the album is there. So I don't know on which side the problem might be. I'm using of both Plugins the latest version in the Extend and the latest version of WP. Thanks for your help!