I have noticed that the plugin will not reapear in outlook if the process is hung.  for example. .

1. the user complains that they can not see the CRM plugin.
2. They close outlook and reopen it (all this time the outlook proceess from the previous session is still running) and still no CRM plugin.
3. If i close outlook and k*** the process ( from task manager) and then start outlook again the plugin reapears!