django 1.4 - can't compare offset-naive and offset-aware datetimes

I am in the process of migrating an application from django 1.2 To 1.4.

I have a daily task object which contains a time of day that task should be completed:

class DailyTask(models.Model):
    time = models.TimeField()
    last_completed = models.DateTimeField()
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=1000)
    weekends = models.BooleanField()

    def __unicode__(self):
        return '%s' % (self.name)

    class Meta:
        db_table = u'dailytask'
        ordering = ['name']

In order to check if a task is still required to be completed today, I have the following code:

def getDueDailyTasks():
    dueDailyTasks=[]
    now = datetime.datetime.now()
    try:
        dailyTasks = DailyTask.objects.all()
    except dailyTask.DoesNotExist:
        return None
    for dailyTask in dailyTasks:
        timeDue = datetime.datetime(now.year,now.month,now.day,dailyTask.time.hour,dailyTask.time.minute,dailyTask.time.second)
        if timeDue<now and timeDue>dailyTask.last_completed:
            if dailyTask.weekends==False and now.weekday()>4:
                pass
            else:
                dueDailyTasks.append({'id':dailyTask.id,
                            'due':timeDue,
                             'name': dailyTask.name,
                             'description':dailyTask.description})
    return dueDailyTasks

This worked fine under 1.2, But under 1.4 I get the error:

can't compare offset-naive and offset-aware datetimes

due to the line

if timeDue<now and timeDue>dailyTask.last_completed

and both comparison clauses throw this error.

I have tried making timeDue timezone aware by adding pytz.UTC as an argument, but this still raises the same error.

I've read some of the docs on timezones but am confused as to whether I just need to make timeDue timezone aware, or whether I need to make a fundamental change to my db and existing data.