Due to the fact CEGUI::WindowFactoryManager does not take ownership of WindowFactory objects registered with it, there is a real potential for issues and exceptions being thrown because client code may destroy or otherwise remove the WindowFactory before CEGUI is done with it (i.e. Window objects still exist that require the factory to be present for final object deletion).
Probable best solution is to allow CEGUI to take ownership of WindowFactory objects. While there are various solutions to taking ownership of subclassed WindowFactory objects from a base class WindowFactory ptr/ref, a template based approach is very favourable here.
Reproducibility: have not tried
Additional information: See original report and discussion here: http://www.cegui.org.uk/phpBB2/viewtopic.php?t=3661