Drupal Twitter Module Error Message: Could not obtain a valid token from the Twitter API. Please review the configuration.

I recently encountered this message while trying to use the Drupal Twitter Module to access a twitter application:

Could not obtain a valid token from the Twitter API. Please review the configuration.

CAUSE

The message was caused by the Callback field in the twitter application setup not being filled in.

SOLUTION

Enter the following in the Callback field

http://127.0.0.1:8000/twitter/oauth

SOURCE:
Twitter 7.x Module Installation (http://drupal.org/node/1346824)