Why does this 7D video flicker?

I've seen this same type of flickering on other people's DSLR videos online. Here's mine taken with the 7D:

http://vimeo.com/13751361

About 12-15 seconds into the video, it does a horizontal type flickering. Is that due to a wrong shutter speed? Am I panning too fast at the wrong shutter speed? I've seen...

WOOPS - as I'm typing this, I just realized that I has the IS turned ON. Would that cause this type of banding?

Thanks!

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