I set up a Homegroup with my old PC so I could pull over my music and movies. I am able to see and copy my videos over, but the music folder keeps giving me the "refers to a location that is unavailable" error.
Check your security options on the admin user of the home group, could be that you are missing full access rights on all users. But usually a security issue wouldn't refer you to another folder, so its possibly something else that's caused this.