What could cause this? f12:
(the f12 has fewer samples, but even when the viewport is at lower samples it looks different..)
I know about color management, but that is at the defaults..
EDIT: oops.. I know 'log' is not a default, but that is because I was fiddling with it. The image above is rendered with 'default'
The material is quite simple, only a translucent shader. (for testing) I even tried appending everything into a new file to reset all the settings, but no difference.
EDIT2: Uploaded blend http://www.pasteall.org/blend/22200