[Serusers] Bizarre behavior of t_relay_to_tcp()

I have had SER working fine for over a month now, but after a reboot yesterday, it exhibited a bizarre behavior as follows: t_relay_to_tcp sends INVITE from the wrong IP address. I have a dell server with 2 network cards each with its own IP address. SER is listening on one of them (listen=<IP> in ser.cfg) and there is no problem with incoming requests. However, SER sends outgoing INVITEs with the wrong IP address. This was not the case before and I have had it working across several reboots. If I replace t_relay_to_tcp() with just t_relay(), it works fine but I need SIP over TCP and hence need to use t_relay_to_tcp() How do I get t_relay_to_tcp() to use the proper IP address for sending SIP messages? I tried rebooting couple times, just to ensure that this was not some transient problem, but it id not change the behavior.