I am running 4k AOC screen which should run at 60Hz ! Before upgrade was ok but now refresh rate is 30Hz and I cannot change it. Gaming is now very lumpy. Need to have correct refresh rate set.
OK this is fixed ! You have to run NVidia driver 353.62 ! This allows me to run at 3840 x 2160 and I get 60Hz. Obviously later drivers do not work correctly in Windows 10.
I found other people with same problem and this has fixed it.
Try updating your monitor driver. When I upgraded it done the same to my pc.
When I put my ultrawide drivers in I got my refresh rate back.
Hope this helps.
The reason I'm suggesting this is because the upgrade may have affected the gpu driver and using the DDU will give you a totally clean platform to start from.
Hmm I'm not too sure how to 'force' in a driver apart from the usual add and remove stuff. See how you get on with using the DDU. I did a little search to see if this version of win 10 was breaking other users refresh rates too and although I didn't find much evidence of that i did find a couple of threads where the user had fixed the issue by replacing drivers so it's worth a try at least?
The only other thing i can think of and have seen in my searches is that other users experiencing the same issue (not with this os exactly) rolled back to the previous version of windows which then fixed the error. It's perhaps a last resort kinda thing but it's an option.
So that was the answer after all... Well I'm glad at least your back to normal but a shame about the new os. Hopefully in a month or so they may have patched it?