I\'m using Internet Explorer 8 beta 2.
Client performs POST on http://alpha/foo
Server responds with redirect to http://beta/bar
I believe that IE8 uses a separate process for each window. If you're using session cookies, the new process will start with a fresh session and therefore won't be able to submit the session cookies received by the other process. Can you try using persistent cookies and see what happens?
From http://www.microsoft.com/windows/internet-explorer/beta/readiness/developers-existing.aspx#lcie
Loosely-coupled Internet Explorer (LCIE) is an architectural effort to improve the browser by separating its components and loosening their interdependence: most notably, it is an attempt to isolate the Internet Explorer frame and its tabs into separate processes. In Internet Explorer 8, this isolation will bring about improved performance and scalability, as well as more potent methods to recover from problems like disk or system failure.