I have the latest versions of the social and Twitter Tools plug-ins. I have added a twitter account to social but blog posts aren't being sent to twitter. The account in twitter shows up in the my profile and in the social settings and is not disabled.
For me to add an account to social, however, debug mode has to be turned on, but once that happens, the account gets added. Now, though, when a blog post is posted, no link is sent to twitter, nore are tweets being downloaded.
Server's running PHP 5.3.22 on Linux.