I believe Cubase does not let the computer sleep at all, regardless of settings.
edit: BTW the topic appears to be becoming useful… now
It’s just the screens I’m talking about, though - I never put computer or the drives to sleep. C6 would not interfere with screens going into sleep.
Ah, thanks for the clarification.
An earlier build of Kontakt 5 caused huge CPU spikes/dropouts every time there was a tempo change. Perhaps something to investigate…
Even simpler - have you disabled multi processing in Kontakt? Generally a recommended practice.
If Cubase 7 and 7.5 worked well for you only until the last updates and you’re having issues running a few Kontakt instruments Cubase is not the issue sorry.
If its really a GPU issue, one of the ways to stabilise the graphic card is to disable the gpu, memory and power scaling option from within the graphic card’s installed drivers. as these cards are designed for gamers and keeping in mind power saving options etc… the card will scale its performance on load. this split second lag or acceleration tends to screw up lots of stuff, from hardcore rendering to simple stuff like monitoring levels etc… its unfortunately not possible to pin point specifically as its mostly system dependent.
I dont have the specifics for nVidia cards however on AMD’s, within the CCC, there is an overclocking option. what i did was to lower the the gpu clock and the memory clock to its factory minimum. i left the power option initially at default but ultimately lowered it by 5%. its been like that since and all is well.
As for Kontakt, there are certain instruments from within the Kontakt Factory Library which does spike the cpu, even on a single instance of Kontakt. it may not be anything of concern as there have been cpu spikes into the red without dropouts or clicks.
hope this helps. Cheers!!!
Not much help to you, but Cubase 8 is the most stable version in years for me. Couldn’t be happier myself.
I bought Vienna Ensemble in the end to run kontakt and nebula libs and the difference in performance is night and day. When i was runnng kontakt within cubase i had mp off in kontakt and on in cubase. It’s a real eye opener seeing how VEP loads kontakt instances about 10x the speed of cubase. I get an overall smoother cpu performance running VEP as well.
Since using VEP i have a new Cubase/GPU problem where cubase will freeze and audio will drop out for good until you maximise a different tab from windows desktop (for example firefox). The audio will suddenly snap back in really loud for a brief moment and then continue as normal.
Thanks Keyz will try those gpu tweaks.
What version of Windows are you running?
7
I’m not sure then I know in Windows 10 there are some compatibility issues with apps running at the same time as Cubase.
Maybe it has something to do with the settings for releasing the audio driver.
As a practical suggestion:
Problem solving is changing a single variable at a time, starting with the most obvious (or easiest/least costly) first.
Since these complaints seem to be centered on Display/GPU issues, why not spend $30-$40 at a place that accepts 30 day returns and put a GPU in your system that is made by another manufacturer. AMD vs Nvidia. If it doesn’t make a difference, return it. As low risk as it gets.
Not to put too fine a point on it, but if GPU related Cubase issues are making your life miserable but you haven’t tried what I’m suggesting, you should definitely value your time and peace more highly.
For reference, this post is from a guy using Nuendo 7 (the initial release) and running issue free on an 8 core i7 with 4 monitors attached. Runs like a Ferrari.
Worked for me! 
SteveInChicago - OP has a GeForce 250, which I think is a card from the same generation as the one you are using. Perhaps you could post the driver version you are using?
Speaking of graphics card drivers, this utility works great for uninstalling.
Graphics driver installers typically leave all kinds of crap in the places which won’t be touched by “uninstall” from the control panel. You could either go hunt for these manually, or use this utility to clean them up. Whenever you install a new driver version, or a different card, I think it is better to remove the old stuff completely.
Here you go:
It’s a NVIDIA GeForce 210, Driver Version 9.18.13.4174
Thanks for the link I’ll check that out.
Indeed, reading is one of the skills I’ve acquired in life. 
This is not based on a scientific study but I do get the feeling that a majority of people reporting issues with Cubase (particularly graphics related stuff) are running Win 7 and not Win8. Obviously it’s a major hassle and depends what requirements your other software has but trying Win 8.1 might be worth considering.
It seems to me like C8 has conflicts with some Nvidia driver versions :
Imho such a machine is a Ferrari… 
I used DDU not long ago as there were gpu issues with Cuabse 7 as well. Have also used the Graphics acccleration tweak mentioned in a pinned thread.
Card i use is a Geforce 210 driver version : 9.18.13.4144