links messed up after modification of permalinks structure

Hello,
I modified for the first time the permalinks structure (WP1.5) �? using the year/monthnum/day/postname format. Since then the links are messed up :

I get a ‘not found’ message for page links and category links acess from my index page :

The pages links show : <!– http://www.sitename.com/the-page-name/ –>
The categories links show : <!– http://www.sitename.com/categories/the-category-name/ –>

Recent posts still work :
The recent posts show : <!– http://www.sitename.com/?p=7 –>

I’m confused 🙁
can’t find the solution in the codex or forum archive… help would be welcome !

philippe