Well, the plugin, after adding "www" to yahoo url in php file :D, does smush images yet present in media library.
Then I made a proof uploading a new image, all OK
But then on another image it did not smush it at uploading; so I clicked "smush.it now", but it returned:
Could not /home/XXXX/public_html/wp-content/uploads find /home/XXXX/public_html/wp-content/uploads
where XXXX is my ftp username.
I checked file ownership, on new uploaded file the server gives 99:99, and permissions (644) given; i changed thewm to my username:group and to 666.
Well nope, same strange error, just for that jpg...