[Serusers] SER on multihomed host

[Ravi]

Hi,
I am running SER on a host with 2 network interfaces. The behavior I 
observe is that when SER receives a message say REGISTER on
interface 1 it sends the 200OK on interface 2. Due to the way the 
network has been configured, this 200OK never makes it back to the
UA which sent the REGISTER. So I want to make sure that SER sends the 
response back on the same interface it got the message on.
How do I do this? I cannot disable the second network interface. In 
ser.cfg I set "listen" to the IP address of the interface I want to use;
I also set "mhomed" to 1, still no luck. Any suggestions are highly welcome.
thanks,
-Ravi.