I am also having that problem. I have done just that. But the simple example from JMyron simply dont work on my iMac. I have Snow Leopard.
I've also installed an Intel version from this link http://www.jibberia.com/projects/. I found it in another thread, but everything is the same. Strange because when I unzipped the JMyron folder, I found that the file /libJMyron.jnilib had a grey icon with the letters "exec" in it.. This normaly happens when the system doesnt recognize the file. Is it becasue of the way I unzipped it?