You should try using extreme conditions.
I used periodic conditions in the weather file (and there was no internal loads, no ventilation or infiltration) and the period was equal to 24 hours.
The internal space was conditioned and I got the following results for different materials in the external wall composition: http://img593.imageshack.us/img593/109/6khg.jpg (the graph concerns the "Surface Inside Face Temperature").
With the finite different method I got similar results.
Best Regards