Why can't a Drupal user edit a node they created?

Symptoms: An authorized Drupal user loses "edit" access to nodes they've created, even if they have appropriate node (or other module) access permissions. Or, user cannot edit a node that should be editable by them, based on access control or node access settings. No errors or warnings appear in the Drupal log.

Possible Cause: The user does not have permission to use the input filter assigned to the node. (Input filter permissions may have been changed since the node was created. As a result, the user never had, or no longer has permission to use the input filter associated with the node.)

This excerpt from Drupal node.module node_access() function tells the tale:read more »