RAW File conversion with odd color bands

[richmilne]

Rather rarely, in files from a Canon 40D shooting in RAW mode, I am getting images like this when I convert:
http://www.richmilne.com/Images/_MG_2153_web.jpg
The banding can run horizontally or vertically, and be wide like these, or very close together. I happens on several computers, and was not there when I first downloaded and viewed the images some months ago. It happens on different images each time, and seems to be a random event. The same problem happens with the RAW conversion in Lightroom. I have tried deleting the xmp files to no avail.
This is very frustrating and I would be welcome of any suggestions. Sometimes it goes away when I go back to my original downloaded files, sometimes it does not.
Systems have been XP Pro and Vista, and latest versions of programs.
Thanks for any help!
sincerely,
Rich Milne

[Chris Breeze]

I'm sorry but the fact that you get the same results converting the image using Canon raw conversion routines and with Lightroom means that the raw data in the image has almost certainly become corrupted in some way. The most likely cause of this is a faulty memory card, card reader or hard disk. If you have copies of the files which are OK it suggests that the hard disk is the problem. If you haven't done so already, I strongly recommend backing up everything on the hard disk and then checking it for errors.
If the disk is OK then it's possible that something in your workflow has corrupted the raw file. This seems unlikely as most apps don't modify raw files (e.g. IPTC data and raw conversion settings are usually written to XMP sidecar files).

[Clive]

It may be completely irrelevant, but wasn't there a firmware update for the Canon 40D to fix a problem of this nature. Someone posted a fix for existing images, too.