Google App Engine application in URL Frame

We’re working on project, which has several user roles and one of the requirements is that it should be available for different users via different domain names. Apache and other HTTP servers provides simple solution for this issue, but we are using Google App Engine. It does not provide mechanisms for handling domain names, e.g. configuration virtual hosts.
Thus we have used “URL Frame” option for DNS host records. It works fine, but some weeks ago we have found one critical issue: some our functionality does not working in the latest version of IE 8 (it works fine without “URL Frame”).
After some investigation I found that problem in using of django’s HttpResponseRedirect. It returns response with redirection response code (301 or 302) and IE 8 handles it as new request (it does not take into account old user’s session).
So be careful with using django’s HttpResponseRedirect in “URL Frame”.