Django forms and MultipleChoiceField
===

Trying to create a form where you can sign up as a user, and add yourself to one or more categories. Getting an error while doing it:

> TypeError at /users/add-user/
>> 'categories' is an invalid keyword argument for this function

Here's my forms.py:

    class AddUser(forms.Form):
    	name = forms.CharField()
    	title = forms.CharField()
    	website = forms.CharField(required=False)
    	email = forms.EmailField()
    	phone = forms.CharField(required=False)
    	company = forms.ModelChoiceField(queryset=Company.objects.all())
    	categories = forms.ModelMultipleChoiceField(queryset=Category.objects.all())

The last line is the one I'm having trouble with.

Here's my views.py:

    def add_user(request):
    	if request.method == 'POST':
    		form = AddUser(request.POST)
    		if form.is_valid():
    			cd = form.cleaned_data
    			try:
    				p = User.objects.get(email=cd['email'])
    				error = "There's already a user with that e-mail adress registered. Maybe he/she is already here?"
    				return render_to_response('users/add_user.html', {'form': form, 'error': error}, context_instance=RequestContext(request))
    			except User.DoesNotExist:
    				p = User(name=cd['name'], title=cd['title'], website=cd['website'], email=cd['email'], phone=cd['phone'], company=cd['company'], categories=cd['categories'])
    				p.save()
    			return HttpResponseRedirect('../thanks/')
    	else:
    		form = AddUser(request.POST)
    		error = "You can't really submit empty forms. Try adding something useful :)"		
    	return render_to_response('users/add_user.html', {'form': form}, context_instance=RequestContext(request))

If anyone has any suggestions to the problem (or even suggestions in general to improve my code), I'd be glad! I'm a beginner to Django and all help is appreciated.