Check out the suggestions people gave me on my post about the same issue and see if anything helps you. Nothing has resolved my issue so far, but I believe it's because one of my roles will automatically be added if the user is granted a different role. I haven't been able to track down what is causing that to happen, but I'm currently looking into it.

http://www.sqlservercentral.com/Forums/Topic1776987-3411-1.aspx

Thanks,

JimiHaze