Groups and 2-legged OAuth

[stmonkeydoom]

I am having difficulty using the Groups API with two-legged OAuth. For
some reason, whenever I try to get a feed, I receive an
AuthenticationException with the message: Unknown authorization
header. I have triple checked the key and secret. I've included the
xoauth_requestor_id in the url, and I've used a variety of scopes,
including:
'http://www.google.com/a/feeds/',
'https://www.google.com/a/feeds/',
'http://apps-apis.google.com/a/feeds/',
'https://apps-apis.google.com/a/feeds/'
I've even tried doing this in the python api, to no avail. Anyone have
any idea what I'm doing wrong?