Integrity Error

[narrowfail]

Hello, I'm using a custom User model, that is linked to a profile. I got the following error while loggin in.

Traceback (most recent call last):

  File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py", line 199, in get_response
    response = middleware_method(request, response)

  File "/usr/local/lib/python2.7/dist-packages/tracking/middleware.py", line 76, in process_response
    visitor.save()

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 545, in save
    force_update=force_update, update_fields=update_fields)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 573, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 654, in _save_table
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 687, in _do_insert
    using=using, raw=raw)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 232, in _insert
    return insert_query(self.model, objs, fields, **kwargs)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1514, in insert_query
    return query.get_compiler(using=using).execute_sql(return_id)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py", line 903, in execute_sql
    cursor.execute(sql, params)

  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/util.py", line 53, in execute
    return self.cursor.execute(sql, params)

  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 99, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)

  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/util.py", line 53, in execute
    return self.cursor.execute(sql, params)

  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/base.py", line 124, in execute
    return self.cursor.execute(query, args)

  File "/usr/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 174, in execute
    self.errorhandler(self, exc, value)

  File "/usr/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue

IntegrityError: (1452, 'Cannot add or update a child row: a foreign key constraint fails (`company`.`tracking_visitor`, CONSTRAINT `user_id_refs_id_e9c7bb5d` FOREIGN KEY (`user_id`) REFERENCES `users_userprofile` (`id`))')

Thanks