Why is some of my iTunes artwork showing up as black and white?

I have already posted this issue here (Reddit) but I guess I'll make a post here too.

I'm having a major problem with iTunes on Windows 7 (64 bit), where my iTunes artwork is showing up as black and white, and videos play with a majorly distorted output. (http://imgur.com/TQXA9OH)

No idea how to fix this, but if I copy paste artwork in from somewhere else, it works fine, however if I download album artowrk using iTunes' built in feature that automatically does it, 75% of the time the album artwork turns out black and white. What's even stranger is that on my iPhone the artwork is fine, but on my iPod Classic it shows up as black and white too. Videos play fine on both devices, but are still distorted in iTunes.

Can anyone help me fix this? I'm running the newest version of iTunes.