It's the Monitor/HDTV, I think. As Video playback looks great and the HDMI cable is a "good One", but will try swapping it out. The boot screen looks terrible and that is not normally a strain on HDMI cable.
driver issue perhaps, windows is running default vga drivers for the boot screen, that is why you could only use 256 color images when you changed boot screens in xp. Unless I'm mistaken when the screen flicks right after the boot screen it is the video drivers loading