Autoposting to Facebook not working

Hi

The Autopost function is not working, I get this error message, in the error log of the plugin:

April 21, 2012 4:21 pm harounkola post_on_facebook exception OAuthException: Error validating access token: Session has expired at unix time 1333904400. The current unix time is 1335025280.

Any ideas?
Thanks
Haroun