Gateway inherits virtual interface instead of physical interface

[devnullph]

Hi, all. We're running pfsense 2.0.1-RELEASE (i386) and all was working fine for a few weeks when we suddenly encountered a routing problem with our default gateway interface:

Destination        Gateway            Flags    Refs      Use  Netif Expire
default            xx.xx.76.129      UGS        0  2469196  vip17
10.0.0.0/8        10.11.41.1        UGS        0  1904384    em4
xx.xx.76.145      link#25            UH          0        0  vip17

It took us a while to notice that the default gateway xx.xx.76.129 (Internet facing) has "vip17" interface, owned by another host, xx.xx.76.145. It's interface should be "em3", the physical interface connected to the ISP switch.

Any ideas on how to force our default gateway to use the em3 interface? After several hours of Googling and failed troubleshooting, we finally decided to restart/reboot the 2 boxes but problem persisted for both.

Appreciate the help. Thanks.