Can some people verify that you can wear one necklace and one amulet, even if neither one is Gauldurs? Also, mention if you have completed the Gauldurs quest or not.
If you've scrolled a little in that thread i linked, you could've found this picture that i linked there: http://i39.tinypic.com/14skvph.png
I clearly have 2 necklaces (not one amulet + one necklace) equipped and none is the Gauldur one.
What i'm thinking is that the Gauldur amulet messes up something about the necklaces in the game which makes it possible to wear two of them after that quest.