Proxy - wrong IP

Hi, My server has two interfaces, A and B. My NAS is on interface A and I'm proxying to another Radius on interface B. My problem is that FreeRadius is sending packets to the Radius at interface B with the IP of interface A (the listening interface to my NAS). I'm running FreeRadius v2.1.1. I've tried to add another listening interface with the IP from interface B, but no difference (shot in the dark really). How can I force FreeRadius to use another IP for the proxying? Cheers, Jørn