title: "invalid literal for int() with base 10:" But can't see why it is accessing an integer
body: <p>I can't see why in my application i am getting this error. As all primary keys are text fields are integers. Here is my code:</p>
  <p>forms.py</p>
  <pre><code> class EventAttendForm(forms.Form):
       talk = forms.ModelChoiceField(queryset=Talk.objects.all())
       membersAttended = forms.ModelMultipleChoiceField(queryset=Member.objects.all())
  </code></pre>
  <p>models.py</p>
  <pre><code> class Talk(models.Model):
       title = models.CharField(max_length=200, primary_key=True)  
   class Member(models.Model):
       name = models.CharField(max_length=200)
       membership_number = models.CharField(max_length=200, primary_key=True)
       talks = models.ManyToManyField(Talk, through='Event_Attendance')
   class Event_Attendance(models.Model):
       talk = models.ForeignKey('Talk')
       membersAttended = models.ForeignKey('Member')
  </code></pre>
  <p>views.py</p>
  <pre><code> def addAttendance(request):
       #eventAttendanceForm
       if request.method == 'POST':
            eventAttendForm = EventAttendForm(request.POST)
        for member in request.POST['membersAttended']:
              ea = Event_Attendance(request.POST['talk'], member)
              ea.save()
      return HttpResponseRedirect('../../../talks/')      
  else:
      eventAttendForm = EventAttendForm()
      return render_to_response('attendance/addAttendance.html',{'eventAttendForm': eventAttendForm})
  </code></pre>
  <p>I cannot see why I am getting this error. The exact error is:</p>
  <pre><code> Exception Type:    ValueError
   Exception Value:   invalid literal for int() with base 10: 'redirectTest'
  </code></pre>
  <p>RedirectTest is a Talk that I created with my form for the add talk to check that redirection was working correctly. The line of code that it is saying is causing the problem is <code>ea.save()</code>.</p>