If you use Firefox within your ThinLinc session, you may have noticed the “legacy menu” appearing sporadically. This menu is shown at the very top of the Firefox window in the following screenshot (“File”, “Edit”, “View”, etc), and can be frustrating for users since it tends to move UI elements around in the browser:
One way this can be provoked is by running ThinLinc in windowed mode, and then switching away from the client using Alt+Tab. More information on this behaviour can be found in the following bug report:
If you want to prevent this from happening, access the Firefox configuration by entering about:config in the URL bar, and locate the parameter ui.key.menuAccessKeyFocuses. Setting this to false should correct the behaviour.