I discovered a bug in the cutting plane for yt. The buffer, received from my C-code for pixelization, was not transposed, as it should have been. I have fixed it, and what this ends up meaning is that the resultant image is now flipped about a line going from lower-left to upper-right. This is not a huge deal; what is a bigger deal is that the cutting-plane vectors were also not transposed, and because that created a two-component plot, they were previously not correct. Now, they are correct, as of r655.
I've placed example before/after pictures here:
I hope this has not been an inconvenience for anyone.