virtualbox.org

Here is what I see in the GUest Window when booting with a Mate or Cinamon ( Mint) 18.3 iso
the video is not clear Host machine is a Linux mint 18.3
Version 5.2.2 r119230 (Qt5.6.1) or virtual box
JF

Enabling 3D acceleration Fixed the problem
Note : After turning it off again, the problem didn't came back! No logical explanation but I'm ok.

Great, thanks for the feedback. And thank you for marking it as [Solved]...
I guess that something "clicked" in the video card/drivers/vRAM? I've seen glitches like that come and go.