Do you work in AdobeRGB colour-space in CS2/Lightroom? If so images left in this colour space do tend to look dull and lifeless on the net. I had exactly this problem until I was advised to convert them to sRGB before putting them on the web. Go to Image>Mode>Convert to Profile... in CS2 and change to sRGB (actually sRGB:1961 IIRC - I'm not at home). I use black point compensation plus Perceptual as the rendering intent and this seems to do the best job on my images.