Everything is ok in the main config file.
Where is the tinyMCE's static config file and is there configured the path to the image or upload folder?
Solution:
As you might have guessed it was a folder permission issue. Changing module folders permission ftom 777 to 755 did the trick. Now I don't need the static config file and TinyMCE is working ok.
Thanks to everyone who gave even a slight though in their minds about this issue
