I'm really not sure how to describe this problem. I first experienced it a few years ago on my home computer, with some photos I'd taken with my Canon 350D, but never found a solution to it. But now it's happened on my work computer. I shot a bunch of RAW files today with a Canon 20D, but when I view them in Bridge or Photoshop, this posterization thing happens to them. And it only happens when I click on or try to open the RAW file. Below is an example of before and after the thumbnail is refreshed in Bridge, after I simply left-clicked once on the file (I've blurred out the guy's face for privacy reasons). Note the more intense blues/contrast and increase in noise levels. The effects are more noticeable on other files. It happened on two different computers in my office - both running CS3. And it seems permanent. I couldn't find any XML files, so I can't just open the RAW files in PS and tell it to revert back to the camera's default settings, because as far as my computer is concerned, they haven't been modified.