Are you sure your camera has them stored in the picture?
What to you get from
If those specific meta data are not there or there is no IPTC profile listed, then I do not think the string format will find them?
(I am not a professional photographer and cannot find any of my images that have IPTC data, only EXIF in the verbose information. So I have never actually tried to access any IPTC data)
What do you get from
in terms of your delegates, though I am not sure whether some delegate is actually needed or not?
Can you post your image to some free hosting such as dropbox.com and put the URL here?
I am on OSX SnowLeopard and have used MacPorts to load my delegates, but install IM from source.