I don't know if this is multisite-related or not, but I recently migrated a Drupal database to WP and a lot of articles don't generate a valid slug. I use the /%category%/%postname%/ in Permalink settings.
For example: The articles post title is Why this/that?
Generated the following slug: /why-this/that
Wich obviously doesn't work.
When I create a new article it generates a good slug. No problems.
Anyone have a thought on this??