Made a post in the drivers section but I see a lot of posts here regarding this than in the drivers section.
Gonna make it short and sweet, if your having issues with the above mentioned in the subject please post here what interface you are using (eg. DP, HDMI) and the refreshrate setting at the time of it not working.
Then do this, adjust the refreshrate to 60hz and post your results. You shouldn't need to restart, seems to be an issue with HDMI running beyond 60hz.