Tag Archive Not Working

I recently upgraded a site to 2.6 from 2.2, and therefore had to import all the old Ultimate Tag Warrior tags into WP, and made a tag cloud using WP’s built-in functionality.

The problem is, clicking on a tag in the cloud returns a page without any results.

The site:
http://citoyen.onf.ca/blogs/

Example tag page that should have content:
http://citoyen.onf.ca/blogs/tag/musique/

Any ideas what’s wrong here?