Hi,My E90 320i had lots of creaking and cracking sound from the doors and I was initially thinking that the door panels were somehow loose and something inside the panel was causing it. The sounds get worse when driving over uneven surfaces or when driving off from a dead stop. They sound like pop corn popping to me.I initially wanted to send my car to my longtime ICE installer to try to sound proof the panels but I chanced upon my mechanic and he shared with me that this is a common complaint with E60/5 Series owners. The sound gets worse when you drive over uneven roads or when you move off from a dead stop. However, he said that he has a fix for the 5 Series and asked if I wanted to give it a try. His boss who drive a 525i shared with me that he had to use this solution too and it worked for him and many otherof his customers too.Apparently BMW worldwide is aware of this problem too and the solution actually came from them. It involves using a kind of tape (think of it like cellophane tape, sticky on one side and not sticky on the other, and translucent but not as smooth or slippery on the surface) which is provided only by BMW which is stuck all along the upper door frames of the car from the A to C pillar. I told my mech I would give it a try since I had no other solutions in mind and that I was not entirely convinced that my door panels were the cause anyway. So in 10 mins, the tape was measures and carefully applied on one side of my car, and we took my car out for a test drive...guess what, dead silence from the side with the tape. I was already smiling like a fool.We rushed back to the workshop, applied the tape on the other side of my car, and went out again. Total silence!!! My mech said "Its only now that you are convinced you are driving a BMW right?"....hahahhaha....now my cabin is so quiet I am picking out other small creaks from other areas which honestly even my wife who sits beside me cant hear....the cabin is soooooo silent now.All in all, it cost me RM400, freaking expensive for just tape but I was told that the tape cant be purchased anywhere else except from BMW. I am not sure if thats really true, one might be able to experiment with other types of tape to see if they work at a fraction of the cost (3M products are your best bet), but I am convinced that the method and tape that my workshop used does indeed work flawlessly and because of the translucency and texture (this tape can be applied on any body colour and it will seem to just blend it) of the tape, it is almost not noticeable at all.Not too sure how many of the brothers and sisters here face this issue, but I hope this helps you in finding a solution. Happy Driving!:rock: