YouTube causes crash to lock screen

YouTube causes crash to lockscreen

I've just clean installed Win 8 a few days ago, then upgraded to Win 8.1. Everything works fine, except that when I watch a video on Youtube, at the end of the video (and sometimes in the middle of the video) the screen goes blank momentarily and then I end up at the lockscreen. When I log in, all the windows and documents that were open are gone. The computer is not doing a full reboot, just a complete log out back to the lockscreen. Computer works fine other than this. Any ideas what to look at? Thanks

I suggest that you look at the power options: Control Panel ->Power Options. Make sure it does not set to sleep mode after a certain interval. Even you are having the video running but without activity on keyboard or mouse, Windows considers it to be inactivity.

I've set it to not sleep, it still exhibits the same behavior at the end of the video. Also if it was in sleep mode, I don't expect all the open applications would get closed.
By the way, I am using the desktop version of IE.
Thanks

I've just tried disabling my Norton protection, did not make a difference. I also tried starting a YouTube video and immediately jumping to the last 10 seconds of the video, and again, it crashes back to the lock screen at the end of the video. So it does not even need to play the whole video, something about the end of the video is doing it.

Maybe I need to flip that setting for hardware acceleration. Where do I find that?

When I look for it in this location
http://www.thewindowsclub.com/hardware-acceleration-windows-7
I don't have a Troubleshoot tab, where the slider is usually located.

Thanks

The video adapter is the Intel 965 Express chipset, and device manager says this is the most up to date driver available.

If it does not have the trouble shoot tab then your hardware does not support it. Try open the video, right click on the video->Settings. If the accerelator is enabled, disable it to see if it improves.

When I right click on the video, instead of the usual Flashplayer options, I am getting what I guess are HTML5 choices, since the last one on the list is "About The HTML5 Player". Not sure what to do with that.

Using Mozilla Firefox, maybe related to this new plug in

I've installed Chrome and Firefox, YouTube videos play fine in them, also apparently in HTML5 which I guess, from the reading I did, is what YouTube is defaulting to now.

So the issue seems to be about the way IE11 is playing HTML5 videos. I wonder if it is related to this being old hardware, this is a Windows Vista era laptop that I clean installed Win 8 on.