arp flip flop

[steptan]

I have a mixed network of FC3/4 / FreeBSD machines. The FreeBSD machines report the following errors in their messages log file for the Fedora Core 3/4 machines:

(FC4)
Nov 9 15:26:40 web03 kernel: arp: 10.11.1.88 moved from 00:e0:81:30:11:66 to 00:e0:81:30:15:73 on fxp0
Nov 9 15:26:40 web03 kernel: arp: 10.11.1.88 moved from 00:e0:81:30:15:73 to 00:e0:81:30:11:66 on fxp0
Nov 9 15:26:40 web03 kernel: arp: 10.11.1.88 moved from 00:e0:81:30:11:66 to 00:e0:81:30:15:73 on fxp0

[/sbin/ifconfig output, clipped, public IP obfuscated]

eth0 Link encap:Ethernet HWaddr 00:E0:81:30:11:66
inet addr:10.11.1.88 Bcast:10.11.1.255 Mask:255.255.255.0
...
eth2 Link encap:Ethernet HWaddr 00:E0:81:30:15:73
inet addr:222.22.139.88 Bcast:222.22.139.127 Mask:255.255.255.192
...

Here are the kernels:
2.6.11-1.1286_FC4smp (dual opteron x86_64)
2.6.11-1.14_FC3smp (singe Pentium4)

When it flips the IP address to the wrong interface (as seen by arp, netstat -nr) sometimes problems occur, sometimes they don't (!?). I've been banging my head against this problem on-and-off for weeks.

Thanks.