Since r72079 the Event Log viewer of ReactOS uses the ScrollWindowEx API with the SW_SCROLLCHILDREN flag to be able to scroll an entire subwindow and its children within a dialog or a window pane. See the attached screenshots for more details (events dialog on the right, or lower pane below the listview in the main window).
Everything works correctly on Windows 2000, 2003, 7 and even on Wine (tested separately), but this does not work as expected on ReactOS. It appears that the controls are misplaces and cause repaint glitches. See the pointed parts in eventvwr_ros_r72071_72079_broken.png