Comment: web address != to physical directory, install problem

Also, regarding your suggestion for $context['self_url'], i will test following update of shared/global.php during coming days:

// the url to be used for self-referencing in forms
if(preg_match('/.php$/', $_SERVER['SCRIPT_NAME']))
    $here = $_SERVER['SCRIPT_NAME'];
elseif(preg_match('/.php$/', $_SERVER['SCRIPT_URL'])) // not SCRIPT_URI !!!
    $here = $_SERVER['SCRIPT_URL'];
elseif(preg_match('/.php$/', $_SERVER['REQUEST_URI']))
    $here = $_SERVER['REQUEST_URI'];
elseif(preg_match('/.php$/', $_SERVER['PHP_SELF'])) // for PHP as CGI   
    $here = $_SERVER['PHP_SELF'];
$context['self_url'] = $here;