Missing Child Categories

I seem to have lost the ability to view any of my child categories.

I am using
wp_list_categories('orderby=name&show_count=0&hierarchical=true&title_li=&child_of=6');
to show the children of a certain parent which has been working fine for months, but suddenly it no longer displays the children, and when i go to admin>manage>cats, none of the children are there to see, and they are not viewable when editing/creating posts.

I have weekly db backups which i have cross referenced and there are no differences, and all child categories are there, …strangely enough if i run
wp_list_categories();
with no paramters i get ALL parent and child cats, and clicking on the children takes me to posts that have been categorized as such.

So it would appear all cats are intact just not showing anywhere in Admin, or being called as children with wp_list_categories().

I have checked the db tables and the ‘parent’ field of ‘wp_term_taxonomy’ is correct !!

I am lost, and if i do not find a solution soon i will have to recategorize 2000 posts ??

I will happily send anyone my sql dump to better help solve this if needs be.

Any help would be greatly appreciated.

Thank you.