ember-cli, ember-simple-auth: Cannot re-register: `store:main`

currently I'm changing my project from ember to ember-cli and run in a issue I can't get rid of. I am really not sure where the problem is, since I also updated ember and ember-data.

I get the Error:

Uncaught Error: Cannot re-register: `store:main`, as it has already been resolved.

I'm trying to load a user via the simple-auth Session.

import UserSession from '../session/user';

export default {
  name: 'user-session',
  before: 'simple-auth',
  after: 'store',
  initialize: function(container, application) {
    container.register('session:user', UserSession);
  }
};

and the session:

import Session from 'simple-auth/session';

export default Session.extend({
  setup: function(authenticator, content, trigger) {
    // Do not let setup trigger
    this._super.call(this, authenticator, content, false);
    // Lookup user and trigger events ourselves
    var store = this.container.lookup('store:main');
    console.log(store.find);

    var self = this;
    store.find('user', content.userId)
      .then(function(user) {
        self.set('user', user);
        self.trigger('sessionAuthenticationSucceeded');
      }, function() {
        console.log('ERROR: Could not resolve user of session!');
      });
  }
});

the store.find is there but then the error breaks it.

I also tired to inject the store like this: Ember-Simple-Auth currentUser example help required but had the same result.

Further I tried to make it via the instance-initalizer for ember-data beta.19. I do stuff like this:

Session from '../session/user';

export default {
  name: 'user-session1',
  after: 'ember-data',
  initialize: function(container, application) {
      var store = container.lookup('store:main');
  }
};

but this ends up in:

Uncaught TypeError: container.lookup is not a function

Using:

 DEBUG: -------------------------------
ember.debug.js:4874DEBUG: Ember             : 1.12.1
ember.debug.js:4874DEBUG: Ember Data        : 1.0.0-beta.19.2
ember.debug.js:4874DEBUG: jQuery            : 1.11.3
ember.debug.js:4874DEBUG: Ember Simple Auth : 0.8.0
ember.debug.js:4874DEBUG: -------------------------------

Thx for the help