diff --git a/account/forms.py b/account/forms.py
old mode 100644
new mode 100755
index 1558bb8..1acf493
--- a/account/forms.py
+++ b/account/forms.py
@@ -7,12 +7,26 @@ from django import forms
 from django.contrib.auth import authenticate
 from django.utils.translation import ugettext as _
 
+class UsernameField(forms.CharField):
+    """
+    The username field makes sure that usernames are always entered in lower-case.
+    If we do not convert the username to lower-case, Django will create more than
+    one user object in the database. If we then try to login again, the Django auth
+    subsystem will do an query that looks like this: username__iexact="username". The
+    result is an error, because iexact returns the objects for "username" and "Username".
+    """
+    
+    def to_python(self, value):
+        value = super(UsernameField, self).to_python(value)
+        value = value.lower()
+        return value
+    
 
 class LoginForm(forms.Form):
-    username = forms.CharField(max_length=255)
+    username = UsernameField(max_length=255)
     password = forms.CharField(max_length=255, widget=forms.PasswordInput,
         help_text=_('Cookies must be enabled.'))
-
+        
     def clean(self):
         username = self.cleaned_data.get('username')
         password = self.cleaned_data.get('password')
@@ -79,7 +93,7 @@ class PasswordForm(forms.Form):
     def clean(self):
         cleaned_data = super(PasswordForm, self).clean()
         old_password = cleaned_data.get('old_password')
-        username = self._request.user.username
+        username = self._request.user.username.lower()
         user = authenticate(username=username, password=old_password)
 
         if not user or not user.is_active:
diff --git a/account/locale/de/LC_MESSAGES/django.po b/account/locale/de/LC_MESSAGES/django.po
index ba122c0..cb9f6c9 100644
--- a/account/locale/de/LC_MESSAGES/django.po
+++ b/account/locale/de/LC_MESSAGES/django.po
@@ -206,7 +206,7 @@ msgstr "c-lab-PIN"
 
 #: templates/clabpin.html:8
 msgid "Change your c-lab PIN to access the c-lab in the basement."
-msgstr "PIN ändern für den Zugang um c-lab im Keller."
+msgstr "PIN ändern für den Zugang zum c-lab im Keller."
 
 #: templates/gastropin.html:5
 msgid "Gastro PIN"