Hi Arnaud Mélon
I just chatted with an supporter. He told me that I should go through this issues: http://helpx.adobe.com/x-productkb/policy-pricing/activation-network-issues.html
Like he said, I checked everything there. But it didn't changed anything. My hosts file is now looking like this:
I also deleted the opm.db file in the user library, like you mentioned in another post.
I just created a new admin account on my Windows PC & tried to start the applications there. But there is also a "Trial"-window who shows up on start. Clicking on "License this software" brings me also to a form where I can enter a serial number.