I have a Drupal 7.14 installation and followed the install instructions in Domain Access readme, install and quick install guides. I added the include statement ("include DRUPAL_ROOT . '/sites/all/modules/domain/settings.inc';") and that is the correct path to my domain access module; I get the error when I try to enable the Domain Access module only - without any of the companion modules.
Don't have any crazy modules loaded (CTools, Devel, Views, CAPTCHA, CKEditor). Hosting environment is plain vanilla shared hosting at 1and1.