Under power options the monitor is set to turn off on 15 minutes. updated my Shockwave Flash to 10.0 r42 when a flash video is played in any of of my browser and the browser is shut down the monitor does not shut down in 15 minutes. the computer has to be rebooted and then everything is fine. reinstalled Shockwave Flash 9.0 r124 for firefox opera and the situation is ok.
install_flash_player_ax.exe for Flash 9.0 r124 did not work for internet explorer since a pop up window said it was a out of date version. 9.0.260.0 version worked ok.
can not understand why the new flash causes this problem. computer exceeds all of adobe requirements. used the adobe uninstaller and then reinstalled.