Premature end of script headers

Drupal 7 + Node access node reference + magic = Premature end of script headers // Internal Server Error (500) // Segmentation fault!

Hello Drupal developers, yesterday I had a lot of trouble with a magical

Internal Server Error (500)
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, [no address given] and inform them of the time the error occurred, and anything you might have done that may have caused the error.