$civicrm_root value not honored when pointing to /sites/all/modules/ in Drupal 5.1; Broken Image Elements

With a fresh install of CiviCRM 1.6 and Drupal 5.1, CiviCRM image elements are broken as they incorrectly point to the .../www/modules/civicrm/i path, not .../www/sites/all/modules/civicrm/i , where the module is installed. I have $civicrm_root correctly set to match the /sites/all/modules/civicrm path to the module, but it does not seem to be honored. The only resolution to this issue that I could find was to move the module into the core .../www/modules directory. This is not generally considered best practice as this directory is reserved for core modules in Drupal 5.1.