Aloha,
I tried Wireshark on my home Apple Intel IMAC using Leopard 10.5.7 and found that I could not capture anything as an administrator. The interfaces did not show up, and I saw an error stating that permission on /dev/bpf0 was denied. Apparently this program must be run as root because the permissions on thios file are crw------- root wheel. However, MAC OS X does not have a RunAs command like Windows does so I found a program called Pseudo that enables me to run WireShark as root just like Windows admins, and now the interfaces show up and I can capture packets.
Best Regards,
Ed Wagner
Mililani, HI