Why is there a green screen flash before playback on desktops?

Green screens in flash typically mean there is a problem with flash video content on the viewer's side, rather than something directly related to the source. To get rid of this, if your computer is experiencing it, right click the video and go to SETTINGS and then uncheck "ENABLED HARDWARE ACCELERATION". That should avoid the green screen problem.

Below are screens that were taken from doing this over a PC: