Replicator in Workflow gives Error Occurred

Question

I have a very simple workflow:

I am trying to create 2 tasks in a replicator.

public sealed partial class Approval_Workflow : SequentialWorkflowActivity
    {
        public ArrayList Approvers = new ArrayList();

        public Approval_Workflow()
        {
            InitializeComponent();
            Approvers.Add(@"test\test");
            Approvers.Add(@"test\test2");
        }

        public Guid workflowId = default(Guid);
        public SPWorkflowActivationProperties workflowProperties = new SPWorkflowActivationProperties();

        private void createTask_MethodInvoking(object sender, EventArgs e)
        {
            TaskId = Guid.NewGuid();
            TaskProperties.Title = "Review " + workflowProperties.Item.Title;
            TaskProperties.DueDate = DateTime.Now.AddDays(1);
        }

        public Guid TaskId = default(Guid);
        public SPWorkflowTaskProperties TaskProperties = new SPWorkflowTaskProperties();

        private void replicatorActivity1_ChildInitialized(object sender, ReplicatorChildEventArgs e)
        {
            ((CreateTask)e.Activity).TaskProperties.AssignedTo = e.InstanceData.ToString();
        }
    }

The createTask_MethodInvoking is hit twice. The first time with the value of TaskProperties.AssignedTo set as test\\test and the second time set as test\test2.

However I have 1 task in my task history list. The second task is not there. In the workflow history I have:

Status: Error Occurred

What could be going wrong? Stepping through the code does not giveany errors.

I added a third user to the Approvers Array List. The code still fails after leaving the createTask_MethodInvoking for a second time.