Dell Inspiron N5040 Brightness Control not working with TeamViewer

Pressing the <Fn> and <F?> keys can only move up and down two levels and the screen is extremely dim...

• Go to the Device Manager, open Monitors, 
• right click on PnP-Monitor (Standard)
• select Properties and check if the Manufacturer is "TeamViewer GmbH"
• Uninstall this driver if it is the case and the system should restore the default monitor driver