RE: M6500 blackouts, new information and question
I set Nvidia PowerMizer Manager as shown here:
Now when the screen blacks out, everything else continues running. From another PC, I can connect TeamViewer to see what's supposed to be on my screen. (TeamViewer has an option to display a black picture on the screen of the computer being controlled, but I don't use it, and besides, blackouts occur before I try to workaround with TeamViewer.) Using TeamViewer, I can go to the M600's Start menu and click menu entries to hibernate the machine. Then I press the M6500's power button to awaken from hibernation, and it does ... to a black screen. The BIOS displays its screen, Windows displays that it's starting to boot, and then Windows remembers that it blacked out the screen so it blacks it out again. Again TeamViewer works, thanks to PowerMizer manager telling the Nvidia driver to keep running, but the blackout doesn't get fixed.
But if I use TeamViewer to reboot the PC then the screen works after rebooting.
Dell System and Device Manager says that keyboard hotkey Fn - D turns the display on or off. Well, if Windows hasn't turned off the backlight then Fn - D does turn it off or on. But after Windows decides it wants that backlight off, Fn - D doesn't turn it on again.
Usually Windows turns off the backlight after awakening from sleep, and sometimes after awakening from hibernation, so hibernation at least has a chance of not making me reboot.
But Windows isn't satisfied with that amount of strangeness. I've set Windows power management so that closing the lid does nothing. Of course it actually turns off the backlight but otherwise continues running. So far this is normal, and doesn't relate to problems discussed above. But when reopening the lid, what happens? Sometimes Windows remembers to turn on the backlight ... and displays a black screen with cursor! The internet is loaded with discussions of Windows displaying a black screen with cursor. But Ctrl-Alt-Delete doesn't bring up the blue screen with security menu ... except that if I connect another PC through TeamViewer then the other PC sees my blue screen with security menu, I can open Task Manager, etc., but only the other PC sees all this while my M6500 still has a black screen with cursor. Then I experiment again, using TeamViewer to hibernate my PC, and it hibernates. Then when I press the power button, the BIOS displays its screen, Windows displays that it's starting to reawaken, and then ... black screen without cursor. Windows remembers that it blacked out the screen but forgot that it was supposed to turn on the backlight and only display a cursor, so now it leaves the backlight off, the same as previous problems.
So PowerMizer Manager can work around Nvidia driver breakage but it can't work around Windows breakage.