f.lux is an awesome program which automatically warms and tones down your screen after sunset so that the bright blue light doesn't interfere with your sleep cycle. It absolutely helped with some insomnia I was having and I've used it for years without problems.
However over the last few months I have been experiencing pops and clicks during project playback in Sonar. They went away when I put Sonar in conservation mode (i.e. reduced display updates) which suggested something graphical related. I went through frustrating hell trying to get to the bottom of it, installing and uninstalling drivers, reseating my card in a different slot etc. Nothing worked.
And then tonight I discovered that f.lux was causing the glitches. I don't know why it's suddenly decided to be a PITA, and the audio glitches didn't seem to affect any of my other audio including that in another DAW I use from time to time. But turning it off, the problem went away.
If anyone else is a f.lux user and experiencing glitches, you might want to try turning it off. And if you can't live without it, don't worry, I have found another alternative - SunsetScreen. It has a more detailed set of options, including the option to disable "Check for screen interruption every x seconds," which is seemingly what is causing the graphics card to trigger audio glitches. f.lux doesn't have the ability to disable this constant polling, and so I could not stop it happening.
Anyway I hope this helps someone.