users can't post to twitter

Hi,
I installed today the module, with the latest stable version for drupal6.
As admin (user #1) I can twit using drupal without problem.
If a user of my website attempt to create content, he receive:
An error
occurred when posting to twitter: 401 Unauthorized.

The user and password are ok because the user can see all his tweets.
So all users have the same problem.
any idea?

do you know if the latest dev version solve it?
Thank you.