I have just faced a problem where i wouldn't be able to list the posts in a category. All other categories would behave normally, except this one.
First i found out that changing the name and slug of the category would make the problem go away and come back. Oddly enough, i narrowed the problem to the category name, or so it seems.
Using a name like "Distraí-me", with the accented "i", caused the problem, but changing the name to "Distrai-me" ceases the problem. The code i am using to display the category posts is:
<?php query_posts(array('category_name' => single_cat_title('', FALSE), 'order' => 'DESC', 'orderby' => 'date', 'posts_per_page' => '-1')); ?>
Please note that i am reffering to categry name, not slug. I suspect there is a problem with sanitizing the accented characters in category names (i had a similar problem before with the word "Vídeos", which i solved by accident).
Can anyone help me with this, or help me to open an entry in the trac? (i can't really tell if this has already been reported).