Rhino mock hangs when running 2 mocked methods in parallel (whenCalled stub)

i'm doing a mocked test that waits until something finishes. the problem is ,that i can't run the 2nd method as it waits for the first one somehow.

public interface ITest
   {
       void T1();
       void T2();
   } 

the problem is in calling T2() - it waits for T1 to end. i don't understand why

[Test]
  public void TestThread()
  {
     ITest t = MockRepository.GenerateMock<ITest>();
     t.Stub(t1 => t1.T1()).WhenCalled((mi) =>
        {
           Thread.Sleep(10000);
        });

     t.Stub(t1 => t1.T2()).WhenCalled((mi) =>
     {
        // something
     });


     Task<string> task = Task.Factory.StartNew<string>(() =>
     {
        t.T1();
        return "";
     });

     Thread.Sleep(1000);
     t.T2(); // This hangs until T1 is finished!
  }

Anyone encountered this?