@Truz I had the same issue, but it just magically started working after about 5 days. Hopefully yours starts working soon. I sat on the phone with XBL support for about 2 hours one night, and they ended up referring me to a "gamer profile team" that would contact me in 3-5 days. They never did contact me, but it did start working, so there you go.
Microsoft aware of Xbox Live profile 'Error 801540B7,' working on fix
Dec 21st 2011 10:08AM (Joystiq)