For what it is worth my D70 (no I did not forget the zeros) had trouble exposing a similarly colored rose under what I would call the same conditions based on the info you provided. I took the shots about a month ago and got the same result on 8 of 10, 2 of the shots were exposed better. I believe that this has happened quite often when photographing red flowers. I wonder if it has something to do with the color. It also tends to make the reds more blue. If I was home I would post my results for you to compare. I thought, at first, that maybe something was beginning to fail in my camera but have since not seen any problems.
Marc There are always two people in every picture: the photographer and the viewer.-Ansel Adams