If you’re experiencing this issue, write in to api@twitter.com from the email address associated with the application. Include the consumer key effected and the API policy team wil try to get you set back up as quickly as possible. When you get an email back from the automated system, be sure and reply to that email as well.
When xAuth was originally released, some permissions were granted in a less sophisticated way as we developed soon after. Due to some recent changes, those older grants need to be reconfirmed and upgraded.