This DLC doesnt work.
It was intended to work when the Wii Shop Channel was active, it would appear this error but it was intentional. After installing this wad file, the in game Shop would allow you to "redownload" everything. Since the Wii Shop channel died, it doesnt work anymore. For a while you could still download even with the shop closure if you retried multiple times, now it just kick you out of the shop screen.
To install JD or Rockband DLCs, I highly recommend you to search around a Wii DLC repository.
the "This occurs after you have posted 5 messages on the forums. Your account will be automatically upgraded to 'Newcomer' within the hour, unlocking additional features such as posting links and more." message wont go away