Fatal Error when trying to log in DRUPAL
Can you confirm which version of php you are using? I just realized that the magic php constant "DIR" (which I first used here in beta4) may only work in php versions 5.3 or greater, so I'm guessing you have a version that's below v5.3.

According to the Drupal requirements, the PHP requirement for Drupal 7 is "PHP 5.2.5 or higher (5.3 recommended)", So I may have made a mistake by introducing a construct that's not compatible with some php versions that Drupal 7 still supports. I'll need to fix this, but either way if you can confirm your php version that would be very helpfu