Evt: Permalink activated : Index.php instead of category.php

I made a wordpress theme.
I edit it, but i didn’t see that i fuck the website… So i did a lot of thing.

When permalinks are activated, Category.php isn’t used by wordpress. That’s index.php that’s used instead of category.php.

When I desactive permalinks. Everything works.
I tried to delet and regenerate the .htaccess.
I tried to up to date Wp 3.2.1 to 3.3.1

I find nothing on google.

I found just a clue: WP use “index.php” when “category” doesn’t exist.

Why WordPress doesn’t execute category.php when activate Permalinks

Sorry for my English. But French community aren’t as good as yours.

THANKS !