You might face a problem of applications launching automatically when you login to your Xubuntu machine. In my case it was Pidgin and Google Chrome launching automatically on startup. I have not set them as startup applications.
If you logout Xubuntu without closing the opened applications then it seems that Xubuntu saves the session of opened applications. And, then it opens those applications on all next logins.
I solved it by removing the content of ~/.cache/sessions/ directory. You should also see if you have checked “Automatically save session on logout” in Settings Manager -> Sessions and Startup -> General -> Logout Settings. It should be unchecked.
Thanks to this answer: http://askubuntu.com/a/125729/77805