If you're under 18...
Your privacy settings are most likely the culprit!
By default, Member Content (which is a fancy Microsoft term for user-created playlists like Furbottom's Features) is disabled if you're underage. In the United States, this is anyone who's 17 or below!
** QUICK DISCLAIMER BREAK: If you ARE underage, please ensure you have your parent or legal guardian's permission before attempting to make changes to your privacy settings. **
To check your privacy settings, start at the Dashboard. Highlight the Settings tab, then select the green Privacy box with a picture of a lock. Make sure that the words "Member Content" appear under the "Allowed" header.
If you're over 18, and/or your privacy settings are not restricting member content...
Now that I've told you all this, there IS one other thing that could be giving you trouble.
Any active players who are NOT signed into an Xbox LIVE profile will also keep you from playing Furbottom's Features and user-created levels.
This means that you can't play them if your second controller is a Guest! So make sure all controllers are signed into an Xbox LIVE account.