Had the same problem with Reach and assumed it would be fixed by the time Halo 4 came out.
Error: Name is Blocked
Description: The name of the creator of this file is not allowed on Xbox LIVE.
I assume all that has happened is that while playing some multiplayer game my team was winning and one of the rumors floating around was that if you report the people for behavior or gamertag they will get a temp ban, and members of the losing team did this out of spite and poor sportsmanship. Is there anyone to contact to have this removed without paying to have my gamertag changed?