Some help please?

I have this weird problem I've never seen before.  This is a cropped portion of an image.  Notice the vertical lines and blotchiness in the blue tones?  I've burned the sky quite dark so this phenomenon would show up a really good here for illustrative purposes, but it exists in my RAW file.  I haven't spotted this, so there is some noticeably sensor dust, but it's the larger patches of darkness and vertical lines in the sky that I'm concerned about.  Is this some natural phenomenon?  Or is there something wrong with my camera or lens?

Thanks,
Travis