I truly must be blessed, I have NOT had that issue at all with 10 Pro and I am very happy with the OS.
I've seen it happen in Internet Explorer alone, flicker flash like crazy and not for a while although sick these last few weeks so haven't been on as much. I'd blame this on both- my reasoning? On 8.1 since a major Norton update, I was having IE crashes (related to flash.ocx mostly) but more critically explorer.exe, without any warning or real stress on programs, sometimes ages away. Did full hardware tests, SFC/DISM were clean- I've updated and knock on wood but no explorer.exe crashes at all for weeks in Windows 10. IE went back to the same crash/no real stress mess after a Flash update.
I'm putting IE aside for a few weeks and running exclusively with Firefox. I think Microsoft has a case as much as Norton's does, especially on it happening with multiple programs as a specific problem/issue set and if I can ride out on Firefox until they release a fix.
I ran into this issue on my primary computer when I was trying to change themes for my multi monitor set up. As long as I used just one background for all three it was fine. I was alerted by the notification bar that icloud was having a problem with it's storage location. Since I don't need or use icloud for this computer I simply deleted it and that seemed to clear up the problem. I can now load themes and they show a different pic on each monitor. If I had only one monitor or never tried to change the background I would most likely never known there was an issue. But I can tell you while the screen was flickering back and forth it was a real pain trying to get it stabilized long enough to reboot, which would usually fix the problem. The only issue I have now is that I have to change the extension of any theme I download and remove the "desk" part of the extension for it to be recognized as a theme.
I experienced this partially in only 1 of my 2 Win 10 Pro's. The Logon/Welcome screen will flash once only once user name/password entered and the Enter key depressed. Not sure if this is related to this though as this machine has McAfee Total Protection Beta and there have been no reports on their forums of this particular bug. Besides the software is Win 10 compatible and was installed after upgrading from Win 7 (which also displayed the single flicker at login....weird).
I'm inclined to think it may be a corrupted registry key inherited from Win 7. I had used Win7Logon Screen Changer on that and the flicker started with the use of that software. The reason I'm posting this is maybe some people have upgraded from another OS using similar logon screen changing software, and in any case my issue was only a single flicker of the logon screen, not the incessant flashing talked about earlier.
No problems here. I feel bad for whoever has this issue, though!
Never had this problems they say, i don't use Norton don't use apple crap and i don't have an intel/IDT sound card. Anyway many of these problems'll get solved in October's release