Can't speak of other operating systems but on Windows 7 : slide-show mode of the Windows Picture Viewer, even when the system is set to ICC viewing environment, doesn't do proper color management. On the other hand, the preview mode should be nearly identical to Photoshop if the settings are correct. However, if your CS4 is unnaturally yellowish, you might consider redoing the monitor profiling. In case you're using Spyder 2s - they don't seem to handle wide-gamut displays correctly.