I am getting the Error at your step 6
[6. There should be an Export option there, select it. Since you have downloaded the Export Key the game will allow you to download the Lego Rock Band tracks to your hard drive.]
When i select the export option and click purchase Right then is when im getting the Error:Unable to access content from Xbox live Error Code 800700e8...
Is there anything else i can do? and im not the only one with this problem that ive heard of... does Harmonix or Microsoft know about this?