WordPress Visudal Editor Not Working

Hi,

I upgraded wordpress to 3.9.1 then have to downgrade it back to 3.6.1 and the new version is not working with my theme.

Then I noticed my visual editors are not working anymore: there are no buttons and I can’t see anything in the visual editor or be able to change anything. The tab is there but just not usable.

I tried to reupload wp-admin and wp-includes folders, I tried to disable some plugins, or switch to another theme, add this line to wp.config.php: define(‘CONCATENATE_SCRIPTS’, false);, clear browser cache etc. None works.

Could any of you advise how to fix this problem? Thanks very much for your help!