[TYPO3] htmlarea not working anymore, missing 'edit in richtext..' button

[Jacky]

Hi all,

(on typo3 4.0)

I don't get it. I was making changes to my page tsconfig and to the .css 
files, but suddenly my htmlarea stopped working. The button 'edit in rich 
text editor' dissappeared and the htmlarea editor also. I copied back the 
originial page tsconfig from a similar installation. Imported a backup of 
the database. Un/Reinstalled htmlarea, no effect.

Tried installing the old RTE extension, but that returns :

"Error: The extension can only be installed in the path typo3/ext/ 
(lockType=G) "



Anyone with tips what I could try to get the editor back working?

tnx in advance
regards

Jacky