[wp-hackers] Problem getting categories

[Brian Fidler]

I'm working on an artists website where I have categories set up like this:

Paintings
   -collection1
   -collection2

Prints
   -collection3
   -collection4

Once I have the category I want to loop through all posts in that category
to grab a custom field from each post.

my url string looks like this:

http://www.mysite.com/paintings/collection1/post-name
http://www.mysite.com/prints/collection3/post-name

I'm trying to get the categories using this:

$categories = get_the_category($post->ID);
echo $categories[0]->cat_name;

It gets the parent category (category[0]) without any problem however it
isn't getting child categories at all.

What am I doing wrong?

thanks
brian