Guys,

i have had boot rattles, please have a look at
http://www.xoutpost.com/bmw-sav-foru...-rigidity.html

Bare in mind, this problem might not simply be confined to the cargo cover only. Mine was to do with Upper/ lower lids. The dealers have adjusted and put felt pads in appropriate places and have sorted these rattles now.
After driving another E70 3.0Si, 3.0D and another 4.8i from the dealer, I am now convinced that the flexing of the body on BMW E70 is quite normal. The rattles are caused by plastic trims rubbing agains with each other when the body is flexing during travel over un-even roads. You may get tailgate, upper lid rattles if the latches are not adjusted approriately. I was surprised all X5's I test drove had boot rattles recently. (My dealer seems to have made sure that they provided onces without any rattles for test driving prior to my purchase)