'Headers Already Set' error after password reset

[anonymous]

I'm running the latest version of the AccountManagerPlugin, r11364, and Trac 0.12.3. After creating a user account and logging in as that user (to work around #9252 / #9843), I reset the users password to force them to change it on first login. When the users logs in, they see the following error:

Upon then navigating to any other page, they are redirected to the page and force to change their password:

Traceback:

2012-04-03 16:43:07,069 Trac[main] ERROR: Internal Server Error:
Traceback (most recent call last):
  File "/usr/local/python26_trac12/lib/python2.6/site-packages/Trac-0.12.3-py2.6.egg/trac/web/main.py", line 522, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/python26_trac12/lib/python2.6/site-packages/Trac-0.12.3-py2.6.egg/trac/web/main.py", line 269, in dispatch
    self._post_process_request(req)
  File "/usr/local/python26_trac12/lib/python2.6/site-packages/Trac-0.12.3-py2.6.egg/trac/web/main.py", line 365, in _post_process_request
    f.post_process_request(req, *(None,)*extra_arg_count)
  File "build/bdist.linux-x86_64/egg/acct_mgr/web_ui.py", line 256, in post_process_request
    req.redirect(redirect_url)
  File "/usr/local/python26_trac12/lib/python2.6/site-packages/Trac-0.12.3-py2.6.egg/trac/web/api.py", line 383, in redirect
    self.end_headers()
  File "/usr/local/python26_trac12/lib/python2.6/site-packages/Trac-0.12.3-py2.6.egg/trac/web/api.py", line 321, in end_headers
    self._write = self._start_response(self._status, self._outheaders)
  File "/usr/local/python26_trac12/lib/python2.6/site-packages/Trac-0.12.3-py2.6.egg/trac/web/_fcgi.py", line 1241, in start_response
    assert not headers_set, 'Headers already set!'
AssertionError: Headers already set!