Thank you thomas, you are right. I read the code of the HELP plugin, the plugin use " int pos = m_pMenuBar->FindMenu(_("Help"));" to find the help menu. When I use the Chinese language pack, the string "help" was translated to "帮助"(sorry I have to use Chinese to describe this situation). So the help_plugin can't find the Chinese string and then can't work well. So, may be I should make a language pack for help_plugin.