there seem to be issues with node middle-click on “retina screen” displays and custom dpi settings. I run windows 8.1 on a macbook pro with a screen resolution of 2880x1800px and a custom “text size” setting of 175%. Middle-clicking on a node results in no action at all most of the time … from time to time it gets me the “new node” dialog and only very seldom the the main menu (f.e. to access the help).
Macbook Pro Retina