Just Copied this from e Photozine. It seems that the apparent problem with the K10D is not exclusive to PENTAX:
Hi, I have had terrible problems with chronic lining/banding appearing on images across all isos.
I sent my camera back to Canon U.K. 3 tmes each time coming back with same problem. Tried different lenes, flash cards etc but no improvement.
As a result I borrowed a camera from my local canon agent in Ireland, tested it, straight away same problem. Only constant between my camera and this one was flash. So rented a 580ex, to go shoot wedding, same problem in the church, I was fit to scream!
I would rate 5d as an unusable camera for the professional. Also Canon U.K. and Canon U.S.A did not appear to know about this problem. I like others had to find out about it on internet. This is a terrible camera and atrocious customer support from canon.
In short I have noticed this problem across various isos starting at 100, with different lenses, memory cards and flashes but indoor shots in mixed light very susceptible to this banding.
The shop I bought it from, B&H Photovideo, would not entertain replacement or refund even though camera was sold in this state and I have repair record to show this. In fact customer service agents very unhelpful there, to the point of rudeness.
What are we poor saps who shelled out a fair whack of cash on these rubbish cameras to do?
see this link for other people who had same issue:
http://www.dslrphoto.com/2006/02/23/...anding-issues/