Failed to write session data (user) (1 reply)

HI there,
There are two hosts in server: interopt and gmdb
The first works perfect
but when trying to run the second it responses with

Warning: session_write_close(): Failed to write session data (user). Please verify that the current setting of session.save_path is correct (f:/wamp64/tmp) in F:\wamp64\www\gmdb\libraries\joomla\session\handler\native.php on line 194

session_save_path looks correct (it's really on f:/wamp64/tmp)

On native.php runs a function like

public function save()
{
	// Verify if the session is active
	if ((version_compare(PHP_VERSION, '5.4', 'ge') && PHP_SESSION_ACTIVE === session_status())
        || (version_compare(PHP_VERSION, '5.4', 'lt') && $this->started && isset($_SESSION) && $this->getId()))
	{
		$session = JFactory::getSession();
		$data    = $session->getData();

		// Before storing it, let's serialize and encode the Registry object
		$_SESSION['joomla'] = base64_encode(serialize($data));

		session_write_close();

		$this->closed  = true;
		$this->started = false;
	}
}

wamp server 3.0.6 64bit
php version 7.010 (the probelm appears when turns on 5.6.25 too)
virtual hosts seems work perfect and host file too


windows 10pro 64



Any idea?

Many thank's
/kostas