TYPO3 Core

My TYPO3 is installed in a subdirectory (i.e. mysite.com/mysubdirectory)

I have an extension with 3 actions (list, new, create) the list action lists extbase models, the new action displays a form to create a new model and the create action creates this model. The fact that TYPO3 is installed in a subdirectory makes it impossible to create a new model. I always have an error that says : "the argument 'newModel' is not set...". If I move TYPO3 to the root directory it works as excepted.

Thanks,

Jérémie