Everything was working fine until 2 days ago ( and I swear that I made no changes!!!)

Yesterday, I went to our website (secretsdupuits.com) and could no loger access it. The error message I get is:

Fatal error: Namespace declaration statement has to be the very first statement in the script in /htdocs/concrete/src/Editor/EditorServiceProvider.php on line 2

The script of that file is:

<?php
namespace Concrete\Core\Editor;

use \Concrete\Core\Foundation\Service\Provider as ServiceProvider;

class EditorServiceProvider extends ServiceProvider
{

public function register()
{
$this->app->bindShared('editor', function() {
return new \Concrete\Core\Editor\RedactorEditor();
});
}


}

I have tried to:

1- remove the space just before " <?php", it does not work

2- I edited the file script to: (found in the latest concrete5 update)
<?php
namespace Concrete\Core\Editor;

use \Concrete\Core\Foundation\Service\Provider as ServiceProvider;

class EditorServiceProvider extends ServiceProvider
{

public function register()
{
$this->app->bindShared('editor', function() {
return new \Concrete\Core\Editor\RedactorEditor();
});
}


}

... and I get the message "Class \Concrete\Core\Validation\SanitizeService does not exist'

Can someone help?

Many thanks in advance !

JF