Keep switching to the main desktop

Yesterday I've got strange issue: the desktop was repainting each 30 seconds or so. If I happen to be on another "virtual desktop" (and application in fullscreen mode) at this moment, I was switched to the main screen (that screen with dock on it). Very annoying.

The issue was connected to Google Drive application. I've clicked it's icon in the top menu, then chosen "Quit" and this behaviour disappeared.

Image on external monitor looks fuzzy

So, you have fuzzy images on your external monitor? Especially in straight lines?

You might need to google around, I'm afraid, but first try to go to monitor's menu and find "Auto adjust" there. Sometimes there's even separate button for this.