[TYPO3-mvc] BE Module shows FE Templates

[Tim Schoch | GSTALTIG]

Hellooo
I've created an Extsion with the builder including a be module. This module worked fine for two days until sudenly* the fe templates get shown. I was working on the controller for the module as it changed. after reverting the php changes to the last state that had worked, the fe templates still get shown. Has anybody an idea or encountered something like this?
Thanks Tim

* you can change "sudenly" with "it wasn't me" or "i didn't touch anything" if you like ;]