The url I used for the internal feed resembles
http://mysites/users/myusername/sub-site-name/_layouts/listfeed.aspx?List=111dcdbb%2Dcffb%2D222d%2Db88f%2D3f0da8da999d#, and works in IE.
The error is "The requested RSS feed could not be displayed. Please verify the settings and url for this feed. If this problem persists, please contact your administrator.", which other questions here indicate might be related to authentication.
This sounds about right as access to our sharepoint is managed through using Active Directory accounts, meaning with Internet Explorer we don't have to login while with other browsers we need to use domain credentials.
So how do I get the rss web-part to "stay inside"? Is there a different url syntax I should be using? or a different web-part altogether?