Post Loop (PB) Widget – Query Arguement not working…

Hi Greg,
Trying to use the loop and not use 2 post catagories… I have read and tried two ways…

query_posts( ‘cat=-3,-6’ );

and one you suggested

post_parent=51

In this support forum (http://wordpress.org/support/topic/post-loop-show-only-pages-with-parent-services?replies=2)

Neither seem to work in that “Additional” area to the widget.
Any help would be greatly appreciated! OR if you could direct me to a post here in the support area…
Thanks,
Leo