Categories not working

On one of my sites, using 1.5, whenever I try to use
<?php wp_list_cats('optionall=0&sort_column=name&optioncount=1'); ?>
OR
<?php list_cats(0, '', 'name', 'ASC', '/', true, 0, 1); ?>

I end up being taken here [http://mydomain.com/?cat=] with no category listed. It means I simply end up back at my front page each time with the full front page list of categories being shown.

Anyone know why that may be?