I'm running Kubuntu 14.04 guest in VirtualBox with Win 7 host. I have video issues. Videos frequently appear on top of everything else, even things they shouldn't - like menus. If I drag a player on the screen, the video stays where it is until I release the player, then the video snaps into the frame again.
I've found that in VLC by changing the video output setting to "X11 Video output (XCB)" I can make the problem go away, but that's only in VLC. I'd like to fix it system-wide, but I can't find any settings. Since I'm in a Virtualbox, I don't believe I have any options on the video card beyond the provided InnoTek VirtualBox Graphics Adapter