Hosted Teamviewer Sites
If your system is currently running a hosted version of Teamviewer, you will get a message saying this when you try to launch the application from the link on the Remote Support page. If this happens, click on Show running TeamViewer
If you are using the old style Teamviewer Interface, your screen may look something like this. If this is the case, click on Connection and then select Exit Teamviewer from the menu choices.