Digital camera image artifacts?

My Canon A620 has started producing images with a region that has artifacts that resemble scan lines. Not every photo has the artifacts, but usually a bunch of photos will have them, then another bunch will not. The artifacts are always in the same region of the image (upper right quadrant). I will attach a crop of one of the original photos that contains the artifacts. The region cropped out was at the left edge of the artifact area, so the right side of the photo shows the artifacts, and the left does not.

Does anyone have any experience with this type of artifact in digital camera photos?

Looks like a CCD problem. Maybe the CCD needs a cleaning or has been damaged in some manner. Though I am not sure how to clean the sensor on a point and shoot.

my 2 cents...

That looks like some form of horizontal aliasing.  I am no expert, so you should research this. But you might change the shot resolution (select a higher resolution?)  or look into an anti-aliasing filter. 

Basically, the camera computer is trying to interpolate the captured image pixels into higher resolution memory image and gets confused in its algorithm.  (actually that sounds like the memory resolution would be too high....)

....or maybe you have a thumbprint on the lens.

I think that any digital image that has snow in it can be a challenge because it messes up the automatic exposure.  For my camcorder I select a snow and beach AE program that counteracts the snow effect.

Thanks for the feedback. The thing is that this artifact appears some of the time, not others, all on the same day of shooting, so I don't think it is something on the lens or something on the CCD. It is always in the same place, too. I even have a sequence of shots where there were several shots without the artifact, then several with it - all from the same session of having the camera on. I almost always shoot at max resolution (~3000 x ~2000). Because the camera is still under warranty, it will probably be most efficient (for my time, anyway) to let Canon worry about it...

Sometimes stuff will show up on the picture depending what f-stop you have. This would be a dirty sensor. I get spots on high f-stop, blue background (like sky) photos. This looks more like a problem with the sensor though and not because it is dirty. I've reading of banding, but don't know exactly what it is.

I once had spots on my sensor that only appeared, as Jason notes, when on small apertures (high f/stops). I had the nice folks at Meier's Phototechnic in Seattle clean it up before a big trip out of the country. I was glad I did, and have not had a problem since. Could be a fingerprint on the sensor? Good luck Charles!