SPListItem.Tasks always empty

Question

I have a custom sharepoint (2007) list (named testlist) on which I attached a test workflow (built with sharepoint designer 2007 and named testwf), which only task defined in the 'Actions' section at 'Step 1' is to wait until april 2014. When I add a new item to the testlist the testwf will start and, when I switch to the grid view, the item has the field "testwf" as running.

Now I need to access the workflow associated with the item and then "complete" this task via code by changing its status but, using the following code, I always get the item.Tasks list empty (but I can see that the internal variable m_allTaskListTasks has 1 element).

        using (SPSite site = new SPSite("http://mysp"))
        {
            site.AllowUnsafeUpdates = true;
            SPWeb web = site.OpenWeb();
            web.AllowUnsafeUpdates = true;

            foreach (SPList list in web.Lists)
            {
                if (list.Title != "testlist") continue;
                foreach (SPListItem item in list.Items)
                {
                    item.Web.AllowUnsafeUpdates = true;
                    if(item.Tasks.Count > 0) 
                       //do work
                }
            }
        }

Maybe I'm missing something...