I've been crazy about the CF door squeak since I got my 20D new back in 2004. My 300D before that didn't have it (and still doesn't), but the 20D made me crazy. After that, my 400D and my 5D also creaked and made me crazy.
I fixed them all.
What I do it take some scotch tape (the clear office tape) put it between the CF door and the body. I open the CF door and put the tape on the inside edge that touches the body. I then use a razor blade and trim the tape by just following the edges of the door, inside and outside edge. In the end, I end up with a layer of tape between the door and the body, and I promise you would never never see it if I didn't point it out.
Problem solved, no squeaking.