I've got a strange problem with my current typo3 installation, I've never had before. I'm not able to access the backend anymore due to the following error appearing when I'm trying to access the backend.
No module found. If this is a temporary error, please reload the Backend!
Thank you very much for your answers! The problem was as simple as it can be. It turned out that my user just didn't have any admin access and that is why I could not find anyone else with the same weird problem. I was told that my account was an admin account, so I didn't even think about this as a possible problem. Sorry guys for bothering your with such a question!
Yours Sincerely, Felix