I see this error message also on my multiwan setup. I have 2 ADSL modems hooked up, one in bridge one in routed mode (same ISP, same network otherwise).
Routing tables
Internet:
Destination Gateway Flags Refs Use Netif Expire
default 88.115.128.1 UGS 0 7966945 em0
88.115.128.0/20 link#4 U 0 0 em0
88.115.135.211 link#4 UHS 0 0 lo0
127.0.0.1 link#6 UH 0 567 lo0
192.168.1.0/24 link#1 U 0 9068001 bge0
192.168.1.1 link#1 UHS 0 0 lo0
192.168.100.0/24 link#5 U 0 0 re0
192.168.100.1 00:14:d1:38:7e:34 UHS 0 148 re0
192.168.100.30 link#5 UHS 0 0 lo0
193.229.0.40 00:1b:21:0a:aa:ac UHS 0 89 em0
193.229.0.42 00:1b:21:0a:aa:ac UHS 0 63 em0
193.229.0.46 88.115.128.1 UGHS 0 204358 em0
193.229.9.190 192.168.100.1 UGHS 0 205264 re0
dmesg:
arpresolve: can't allocate llinfo for 192.168.100.1
arpresolve: can't allocate llinfo for 192.168.100.1
arpresolve: can't allocate llinfo for 192.168.100.1
arpresolve: can't allocate llinfo for 192.168.100.1
I am not using PPoE or anything fancy like that, I have DHCP enabled on both WAN interfaces.
Let me know if you need any other info