bug was already raised in chromium tracker http://code.google.com/p/chromium/issues/detail?id=20574 but firstname.lastname@example.org said that the problem is in webkit.
Short description: position: fixed on child nodes does not work when parent element contains transform or transition property.
check the demo and feel free to ask more description (FF works well with it).
The CSS3 transforms spec says of transformed elements: "The object acts as a containing block for fixed positioned descendants."
mm, so elements with fixed position inside transformed element won't behave as fixed ones?