I'm getting the same error, but different circumstances.
I've set the URL for a dashboard (using IE Plugin) as the browsers home page. When I launch the browser it redirects to a login screen. But, if I go to the Access Point portal it logs me automatically via single-signon as expected.
The first time I launch the dashboard, I get the error you're describing. But the problem goes away after a refresh.
Seems like a long shot that they would be related, but it is the same error message..