I have the same problem with bit.ly. The plugin does tweet the post, but it does so without the shortened URL. Here is the log from a post I manually published a few minutes ago.
[2013-04-11 16:58:19] - [Posted] [Twitter - Unit Forward] - OK - Message Posted
[2013-04-11 16:58:16] - [E] [-=ERROR=- WP_Error Object ( [errors] => Array ( [http_request_failed] => Array ( [0] => connect() timed out! ) ) [error_data] => Array ( ) ) ] -
[2013-04-11 16:58:11] - [Skipped] [Pinterest ()] - -=[Unchecked Account]=- - PostID:664
[2013-04-11 16:58:11] - [Skipped] [Google+ ()] - -=[Unchecked Account]=- - PostID:664
[2013-04-11 16:58:11] - [Start =- ]- ------=========#### NEW AUTO-POST REQUEST PostID:(664) Immediate ####=========------
If I resubmit the post to Twitter (with a change somewhere in the message format to avoid a duplicate message error), the post is tweeted correctly with the SURL.