This lunchtime I upgraded WordPress on the server to 3.1 version
I had a lot of trouble getting WP to Twitter plug-in into work out of the box. I though it was a chroot Apache problem, a missing executable, or some file permission issues with Ubuntu Linux. It was none of the above.
This was a configuration of PHP5 and CUrl module. Essentially I solved this by using Linux administration commands. Become root.
Make sure curl installed
apt-get install curl
Make sure php5-curl is installed
apt-get install php5-curl
Make sure the wordpress area is locked down with permissions
chown -R www-data:www-data /opt/wordpress
Set the permission for wordpress directory so that you as the SysAdmin can upgrade to next version
find /opt/wordpress -type d -print | xargs chmod 775
Restart the apache server with wordpress
Go to the WP to Twitter settings page, perserver with the security keys. Verify that your Twitter consumer keys and my application settings are in agreement. You might have to restart Apache again. It does work. See also here.