Disturbing creaking sounds from Interior, Normal?

[Montecristo]

Hello good X5 owners.

I bought my E70 X5 in august 2007. Its an 3,0 diesel with the sport package and the optional 20in wheels.

My problem is that the creaking sounds from the back seats and around there are really getting to me. The dealer seems reluctant to look in to the matter and i feel somewhat helpless because they claim its normal for the car to flex and the interior to be making noises.

Pleas give me your experiance and opinion about this. Your thoughts about this may give me the perspective I need to fight this through with the dealer.

The car does not have active steering (and thats jolly good I might add). Nor does it have adaptive drive and those clever stuff.