What causes this?

Is this a sensor problem or could it be something else? When I shoot at fast shutter speeds (generally > 1/1000s), i get the light banding as shown below. This is less noticeable at slower shutter speeds. It happens with all my lenses, at any focal length. Any ideas? Thanks!

<ETA> 30D

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From what you've given us, we know this
1. It happens with all your lenses therefore it's in the camera
2. It happens at at the same ISO if you vary the shutter speed- so it's probably not electronics.

This suggests it's related to the shutter... they do sometimes misbehave - maybe yours does not like extremely short exposures. I'd suggest you check the number of clicks and if the camera's still under warranty, take it back to its mummy.

Edit... saw it's a 30D so it's probably time to start looking for a replacement. There's no urgency as long as you find a way to keep the exposure longer than a millisecond.

Edit again... looked at the images again and point 2 is wrong. I suggest you try not to change more than two things at a time .. so exposure and aperture or exposure and ISO or aperture and ISO... but not all three at the same time.

+1
looks like shutter failure

+2

I've seen before on this forum where this is described as an impending shutter failure. It isn't completely gone yet, obviously, but it will be gone soon.

(No personal experience here, just seen similar threads with this result)

+3 your shutter is on the way to failure.

as noted, your shutter appears to be on the way out.

there are shutters for sale on ebay, and here's a video on someone replacing it on a 30d. he claims cost was about $300 to get it replaced, and did it himself for about $40. probably not something i'd try, but if you're up for it people have done it.

http://www.youtube.com​/watch?v=bPWty4XCbe0

Must add here too, shutter is on the way out. Alas, it's only going to get worse if, indeed, that's what it is (and pretty sure it is).