Several of the Pathauto module's placeholders changed between the 1.x and 2.x versions.

If you upgraded from Pathauto 5.x-1.x to 5.x-2.x while preparing your site for the upgrade to Acquia Drupal, review and update your URL generation patterns at Administer > Site building > URL alias > Automated alias settings (?q=admin/build/path/pathauto).

If you were already running 5.x-2.x, the URL generation placeholders are the same in the 6.x-2.x version included with Acquia Drupal, but check your sites's Pathauto configuration page to be sure all is well.