It's likely that you haven't succesfully renegotiated your access token to the application permission level. The easiest way to accomplish this and account for lag is the following:
1) Go to your https://twitter.com/settings/applications page and find your application. Revoke its access to your account. Wait 5 to 10 minutes for all of that to take effect.
2) Go to your app's detail page on https://dev.twitter.com/apps and find the "My Access Token" feature. If it's already in an "open state" with access token keys on the screen, take note of the strings currently presented.
3) Use the "Recreate my access token" button.
4) When you're back on the app detail page again, refresh the page until you see the string representation of the access token change. Make sure that the permission level detailed on the access token is the level you're looking for.
5) Copy and paste the access token and access token secret into your needed location. This is now "YOU" as far as the application is concerned.
Hope this helps.