Mike just check for RF type interference from your cables. I found that bundling the power cables together and the download cables separately pretty much removed this problem with the banding when I was doing DSLR images.
I like the sharpness of the image and guiding looks good, but I am not 100% keen on the colour. When I have viewed this through Tims 22 I saw some hints of green in this nebula. The colour is also verified by the lack of orange stars in your image. There are some there and use these as your guide for colour balance. Usually I find if your stars are the right colours and saturation the rest of the image looks right too.
There is also some faint nebulosity in this image that I can just see with my overly bright screen, but pushing that out might cause the banding and diagonal noise to really leap out.
Good image all the same, especially given you have not imaged it for a while. However, time you did another object though. How many times have you imaged this now?`
