If the user performs an operation and it fails because of a lack of permissions, the error dialog should not only inform the user of this but also allow the user to Authenticate himself and retry the operation.

"Pre" authentication is already in use in ubuntu in the form of the "Unlock" button in admin dialogs.

Allowing the user to retry with more permissions will make life easier.

A scenario of how this could be used:
A user tries to delete a file(s) created by root (using nautilus), the user is then told that the operation failed on a particular file because of a lack of permissions.

The error dialog will then present the options to either "skip", "skip all", "cancel", "Authenticate" and "Authenticate All". When the authenticate options are selected, the operation could be retried with the user rights entered (can even reuse the Authenticate dialog).

"Authenticate All" option will allow the user to make use of the permissions for the rest of the files.

This will save the user time because he no longer needs to go and change the permissions manually after it failed.

Other information:
Note: The above behaviour can also apply to when a user is editing a file in gedit that is located in an area where his current permissions aren't sufficient. Instead of being stuck there user can be asked to authenticate and have the operation retried.