> the scheduler system runs in a backend context. You can create your cObj  
> by simplying calling t3lib_div::makeInstance('tslib_cObj').*
> * ContentObjectRenderer for TYPO3 > 6.0
The keyword "ContentObjectRenderer" lead me to this page: http://pastebin.com/znXm9EhM
It's working now, thanks! :)
Kind regards,
Stefan