Reported for: WPML Multilingual CMS 3.3.8
Resolved in: WPML Multilingual CMS 3.5.2
Visiting the second language on your site – e.g. http://example.com/de/ , may redirect you to the language you have set as default in your browser. In that case, you need to switch back to the language that you have (previously) selected.
At this time, there is no workaround, except disabling the browser redirection on the WPML->Languages page.