I recently upgraded to CS4 and have been experiencing the following problem. When I open an image from ACR to PS CS4 it looks absolutely nothing like it did in ACR. If I was to describe it, it would be that the image has an overall red tint when viewed in CS4. If I then save this image as a PSD file, and then open it in PS CS3 it matches the CS4 ACR image. So, what have I got set wrong in PS CS4 (which is still all of the default settings)?
I believe the whole CS4 series is color managed. If not then it should be. Anyways, CS3 works fine and CS4 does not. That also probably tells us the ACR is not the culprit since I believe you replace CS3's ACR with CS4's when you upgrade.
If you primary monitor is calibrated then you should not have an issue. If you move an image to your secondary monitor then the colors will be off. So just don't edit the images in any other monitor then the primary and always calibrate the primary.
Since many have two monitors with nearly equal characteristics then they probably are unaware of this problem - the color profiles are perceptually almost the same. However, if you are like me with a laptop and large LCD secondary the colors are way off. I have a workaround by making all my final color corrections in Lightroom which works just fine in both monitors.