Q: Cannot use ShowTree in iTunesU API

Hello

I am trying to query the iTunes U API to return a list of all of the details in my iTunes U site.  I am using the /API/ShowTree call detailed in the documentation but I am getting the following XML return:

<ITunesUResponse>

<Version>1.1</Version>

<error>Command not allowed</error>

</ITunesUResponse>

I have been able to do this in a previous site that has not been migrated to use the Public Site Manager so I am wondering if there is a difference in the APIs between versions?  If so is there a new call or better yet an updated version of the docs that I can review to better understand the differences?

Thanks,

Wes