wireshark on Mac only collects a couple of packets

[robin at digininja.org (Robin Wood)]

I've installed Wireshark on the Mac and I'm getting an odd problem
where it will collect  2 or 3 packets then it stops collecting.
Restart the collection and it will grab a few more.

If i run tcpdump then that is seeing all traffic on the interface so I
know there is traffic and that it can be read.

The problem isn't with /dev/bpf files, that bug is not seeing the
interfaces which I can do.

Starting as root doesn't help, that gets the same problem.

Anyone else seen this issue or can suggest how to fix it?

Robin