Banding Problem (It Sucks)

UPDATE: I already called Canon regarding my concern, and they told me not to bring it to the service center yet unless it happens again. Hopefully these bands wouldn't appear again in the future.

Original image. Click the picture to zoom in.

100% crop of the sky. Click the picture to zoom in.

Yikes, having a backlog in posting all my pictures is already bad enough, now this. Can you see the horizontal lines in the sky? That's banding, and it really sucks. I guess it comes out once in a while when doing long exposures or using high ISO, especially on an old camera like my 400D. Now I really have to have it checked at the service center. And saving up for a new camera doesn't seem so bad now.

I posted this problem on several photography forums, and I would like to thank all those who provided their insights. Please check out these threads, maybe you could contribute some answers as well.

PiPho thread
DPP thread
POTN thread

Click the image to zoom in.

Oh, and I also need to invest in a LENSPEN. The filter in my 10-22 has some stains (probably from raindrops) that causes orbs to appear, especially when using a small aperture.

All the photos above where taken at Harbour Square last Saturday. I still don't have time to process the pictures (and still busy processing some other images), so for now please enjoy these shots from George.