If at any point the connection between the client machine and the server is interrupted for more than ten seconds (such as by networking issues, or the IIS Application Pool being restarted), then Users screens will be overlaid with a warning. This prevents an agent from continuing with the Workflow until the issue is resolved, protecting against issues caused by attempting to fire external queries that won't succeed.
The overlay will remain in place until connection to the server is re-established, at which point the User can continue working as normal. If the User refreshes the window or closes the browser while this overlay is visible, then all current unsaved data will be lost - therefore, agents should be directed to wait for the overlay to clear rather than attempting other action.