Unfortunately, the described solution is partial and only works if datasource is placed as a component. If it is dynamically generated, the problem remains.
Based on this, after several tests I can describe better the problem and the solution.

      $myQuery = new Query();
      $myQuery->Database = $this->myDatabase;
      $username = 'testuser'; $password = 'test';
       $SQL = 
      'SELECT * FROM ' . $this->UserLogin1->UserTable . ' ' .
      'WHERE Username = ' . $this->UserLogin1->Database->Param('Username') . ' AND PASSW = ' . $this->UserLogin1->Database->Param('Password');
      $myQuery->Active = false;
      $myQuery->setSQL($SQL);
      $myQuery->setParams(array($username, $password));
      $myQuery->Active = true;
      echo $myQuery->RecordCount; // ! This line forces apache to crash

The solution:

 $myQuery = new Query($this); //only place owner parameter in constructor