Not entirely sure where the error lies, but it seems like there is something wrong with the constructor function or how it passes username/password.
I found I consistently got 401 http response from the Posterous API for http://posterous.com/api/getsites, though I knew my authorization was correct.
What I did was to find the call to:
$data = $this->get_page( $url, $this->username, $this->password );
And hard code in the username and password:
$data = $this->get_page( $url, 'myusername', 'mypassword');
(This was line 105 in the 0.9 version).
That got my past the get_sites call, but then it was failing on getting the posts. (403 status on the call to http://posterous.com/api/readposts).
Realizing my posts (on the posterous side) were public, and didn't require authorization, I just changed line 157 from:
$data = $this->get_page( $url, $this->username, $this->password );
to:
$data = $this->get_page( $url);
I still had to put in the username and password when submitting the form to pass the jquery test, but once I bypassed that I was successfully able to import 50+ posts and over 450 comments from a Posterous site without trouble.
