[ALPS-users] susceptibility problem

Hi everyone, Im new to ALPS so i apologize if my question is silly, however i did not manage to find an answer neither in the mailing list nor on the wiki. I am trying to calculate the magnetic susceptibility of a spin 1/2 ladder in a magnetic field above Hc1. Unfortunately the result i got is very puzzling: The calculated uniform susceptibility differs a lot from the susceptibility calculated as dM/dH. I was using the dirloop_sse algorithm on a 400 site ladder. Is there an easy explanation of this issue? Best, Stanislaw