Are you connecting to the same network via TWO interfaces? (Like: wireless AND wired) And are both of those interfaces on the same subnet?
I occasionally see the same message you are reporting, typically right after I wake my laptop up. And I've realized that -- when I'm plugged into our office wired LAN, and also leave my wireless on -- I actually have two active interfaces on the same LAN.
Right now "ifconfig" shows my en0 as 10.0.5.44 and en2 as 10.0.5.192. Both interfaces have "netmask 0xffffff00 broadcast 10.0.5.255".
I think this explains the periodic message in my case. Bonjour searches for conflicting hostnames when it connects to the local LAN. Problem is, my machine connects *twice*. And the two interfaces do not connect at the same instant in time. So you have a race condition between the two interfaces.
Now that I think I understand why it's happening, I'm lazy enough to live with it. For now.