Excluding Categories not working when Front page set to Static page

I spent all day trying to figure this out, so somebody please tell me what I’m doing wrong. I want to exclude Categories 99 and 101 from my posts page. It works if I set the front page to display recent posts. However, if I set the Front page to a static page the query filter stops working. I’ve tried this one two separate WP installations on two different servers with the same results. Here is my query:

<?php query_posts($query_string . '&cat=-99,-101'); ?>

This has worked for me in the past, so is there something new in WP 3.1.1? Or what could be in my theme that is preventing this query from working? I am filtering out Cats 99 & 101 successfully in other areas of the theme so I know the categories are valid, and their ID numbers are valid. Also, if I add to the query string something like &posts_per_page=3, it will show only 3 per page, so the query_posts does work, but not for filtering categories.

Any ideas?

Thanks in advance!