I have recentely tried installing JoomlaComment however when I click "Add Comment", I get a 404 error saying component not found. My server has PHP v5; what could be the problem?
Try clearing all your cache in the Joomla backend [ Tools -> Clean Cache ] and also for your SEF component. If needed, uninstall JoomlaComment and reinstall (make sure uninstall complete is set to NO in the JoomlaComment backend and backup; as usual)