Hello Rizos, Brandon and TubePress group, and all
I found a way around this issue. The problem is with the foreign versions of wordpress since 4.0.1 that transforme ( "" ) into (» ») in the tubepress shortcodes. So I simple put my shortcodes between <code></code> to force WP not to change anything in the shortcode. And Bang ! everything is working fine.
Exemple : <code>[tubepress mode="user" userValue="ABCNews" resultsPerPage="15"]</code>. Please make sure you are doing this in the text editor.
A minor annoying thing I can live with however is that the videos meta are not formatting properly with the font I chose. All are printed in " courrier " font now.
Good luck guys,