Fike,
I asked for the raw file, not for a JPEG. Anyway, as far as I can see this is the customary pattern noise, some call it banding.
I could have measured in the raw image, at which intensity of the dynamic range this is and compare that with other cameras. Anyway, I guess this is in line with other cameras. The 40Ds are doing that, the 5D2s are doing it, etc; it is probably close to the end of the tenth stop of the dynamic range, you can'r expect better from the 50D.