If you have received this fault as a Hosted ConQuest user, please try selecting CTRL+ALT+END whilst on the ConQuest message, and you should see an option to sign out (sign out of the Remote Session, not your own machine).
If the above is not working, please raise a new case online and reference the title of this article.
If this is running on your own machine, you should be able to use Task Manager to close ConQuest.