Hello, I have been dealing with this issue since August 2013 - it's just soo frustrating.
In my case it is definitely an intel drivers problem. Non of the current drivers did work for me constantly.
Sometimes i might have gotten an image on my extended screen for a few minutes but then monitor turned black again.
Are you willing to send your system to us? No
Is your system a laptop or desktop? laptop
What is the make/model of your system? (COMPLETE model name required) Lenovo Ideapad U410
What is the model of your CPU? Intel Core i7-3517U CPU @ 1.90GHz 2.40 GHz
What is the make/model of your failing display(s)? external Monitor, Samsung Syncmaster P2450
If laptop, is your built-in display failing? (Yes/No) No
What is your operating system? Windows 7 Home Premium
Is it a 64-bit or 32-bit operating system? 64-bit
What display driver version do you have installed? 8.15.10.2656 (this is now working for me), before i tried the latest driver for HD Graphics 4000 (all not working)
What type of connection are you using? (HDMI, VGA, DP, DVI?) HDMI
What happens that results in the blackscreen failure? Everytime when external display turned off a Notification at the right bottom of my laptop display appeared: "NVidia: GPU is ready to turn into power saving mode". One or two minutes after this had happened my internal and external display started to turn off and on again, rearranging everything. It seemed liked the external Monitor was detected, than system tried to establish connection and right after that the connection was killed by another program. And this was going on forever second by second. Only unplugging the external display from hdmi-port made this stop. When i plugged hdmi-cable in again, the described process would have started right over again.
Anyhow, i solved it in my case and i hope this might help others as well:
1. disabeling my Nvidia card in Bios (the option in my case is called:"UMA only"
2. installing the drivers which were originally installed when shipped.
3. for both Intel HD Graphics 4000 and Intel Display Audio
4. use extended display mode
5. power savings are all set on high performance
Driver versions which are working for me:
Intel HD Graphics 4000:
Driver Version: 8.15.10.2656
Driver Date: 17.02.2012
Intel Display Audio:
Driver Version: 6.14.0.3090
Driver Date: 06.12.2011