I just saw some other posts on video quality on newer PCs, so I tried some things.
Amazingly I found that the now quite old slingplayer 1.5 I dug out and installed works fine if I keep VMR ON but disable VMR9, fullcreen is ok as well.
Back to slingplayer 2,4 and video is bad again, with either VRM or VRM9 enabled of disabled.
I did find the only mode video that is good and watchable with slingplayer 2.4 is with VMR off and VMR9 disabled and then click off 'fit to player' so I just have a 640x480 video window in slingplayer. If I make this window fullscreen I get frame skipping with sort of page rolling and one of the four CPU cores goes 100% busy, so I guess video rendering in this mode of Slingplayer 2.4 is a single threaded cpu process, would be a good candidate for multithreading in my opinion.
So I guess for now I will live with this as being limited to watching in a window 640x480 VRM and VRM9 off in Slingplayer 2.4 or go back to Slingplayer 1.5..unfortunately the latter solution looks most promising
I tried my external DVI 1900x1200 monitor on my laptop, same problem
My vote it is a Slingplayer problem.