Error on register new User

[dna]

Hi, i've tried out your plugin. but when register a new user i get the following error:

10:40:00 Trac[main] ERROR: has_user
10:40:00 Trac[main] ERROR: Traceback (most recent call last):
  File "/usr/lib/python2.3/site-packages/trac/web/modpython_frontend.py", line 265, in handler
    dispatch_request(mpr.path_info, mpr, env)
  File "/usr/lib/python2.3/site-packages/trac/web/main.py", line 424, in dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.3/site-packages/trac/web/main.py", line 284, in dispatch
    resp = chosen_handler.process_request(req)
  File "build/bdist.linux-i686/egg/acct_mgr/web_ui.py", line 114, in process_request
  File "build/bdist.linux-i686/egg/acct_mgr/web_ui.py", line 121, in _do_create
  File "/usr/lib/python2.3/site-packages/trac/core.py", line 153, in __getattr__
    raise AttributeError, name
AttributeError: has_user

Trac r2010, Apache2, mod_python.

another question: how to set the position of the "register tab" between login/logout and setting ? on my installation its on the end.