When my W500 is on battery power and idle for 3 minutes the screen will flicker once then when I press a key it will blank briefly again before I can continue using the system. It turns out that there is a power saving feature that is causing this . The battery power default setting is to adjust the refresh rate to 50Hz after three minutes idle.
To change this:
Open the Control Panel and select -> Power Options
Select Power Manager tab then click "Launch Power Manager"
In the "Power Manager" click the "Power Schemes" tab
Next, press the "edit" button to edit the currently selected scheme
(or whichever one you want to remove flicker from)
Press the "Next" button
Finally, click "Lower display refresh rate" under battery settings and select "NEVER"