That's a PSD and you saved it as a JPG. Try saving as PNG and see if it's better. Honestly though I don't see how those two are different... It's possible that the light gray background of PS is making it seem darker. =P
it looks lighter on GR because it is against a darker background. Try puting it against a light background and it will suddenly look darker.
hm..not sure what you see different but looks exactly the same on my TFT - Its all abou BG on which u place it as said