Thanks and Oiling the lock shaft worked well for me
I just wanted to register and say thanks for all the info on this page. I just replaced the door key cylinder on my 2003 325xi. Took a lot less time because of this page. Something that also worked for me though was oiling the lock shaft that goes down the door card (aka door panel) That is, when I replaced the whole cylinder from the hex screw on the side of the door, the inside was so rusted that it only turned part of the way, (my car might have some water-seal problems) and would not unlock. So if you are 100% sure you have installed it properly and the key still won't turn it all the way, try some old motor oil down the lock shaft (the little black button that moves up and down when you unlock the door) and give it a good 15-20 minutes to let the oil work in. I was ready to give up after I oiled it, but then I came back and it worked like a champ. Message me if this isn't clear. Good luck!