Hey everyone!
We've figured out the bug and should be sending out those blocked codes throughout the day today. It'll be a long (and tedious on our end) process but we'll get them all out to you.
Still feel free to write into
support@harmonixmusic.com if you are having troubles, but please do not send more than one request for your code in the next 24-48 hours.
Thanks!
HMXveng
UPDATE: For clarification, as we are receiving numerous e-mails asking for their codes without having registered their copy of the game: In order to receive the download code, you must grab your Rock Band 2 manual, turn to the back, and enter in that code to the website: register.rockband.com and follow those instructions.