Cannot uninstall SABnzb 0.7.11 on ReadyNas 204 - OS 6.6.1

Hello this is my first post here.

I have "SABnzb 0.7.11-0rnx8" installed on my Readynas 204 with firmware 6.6.1.

Since a couple of weeks i have no more write/delete rights on my (temp)sabnzb-download complete and incomplete folder.

I think this is since a FW-update from 6.6.0 to 6.6.1.
I've tried to create a couple of new folders and than replaced them, but that didn't work. So i tried to uninstall the sabnzb-app, but i cant.
I got a message: (translated from dutch)
"application can not be initialised - empty sourcefault . bad NML-call, Code: 22002010000"
Then i thought, maybe i can reinstall the app, but it is not available anymore in the app-list.
Can u please help me to fix this problem? Does someone knows a solution?

Thanks in advance.