Cannot get Instructure SP working with IdP version 3

[shibboleth655 at lewenberg.com]

We are testing a new Shibboleth IdP version 3 installation and have had 
fairly good results so far. However, we cannot get the InCommon SP 
Instructure to work. There is no error on our side, rather, the web page 
on the SP side comes back with a generic failure message ("There was a 
problem logging in at Stanford University").

We are sending the username in the unspecified nameid format in the 
Subject, and an opaque identifier as eduPersonTargetedID, but not much 
else. We send the assertion encrypted and the response signed.

If anyone has been able to get Instructure to work in their Shibboleth 
version 3 IdP environment, please tell me how you did it.

Adam Lewenberg
Stanford University