Something is technically wrong.
Thanks for noticing—we're going to fix it up and have things back to normal soon.
Here is the message on twitter status blog
Working on high number of errors 1 day ago
We’ve been contending with an elevated number of errors since late last night. We’ve ruled out a number of causes of this problem but are still working to reduce the number of errors on the site.
Update (12:35p): We’re continuing to make changes and are seeing errors return to more acceptable levels.
As a action toward reducing the number of errors, twitter team has decided to disable the Retweet feature temporarily.
Retweet feature temporarily disabled 1 day ago
We’re working on a few problems related to the ongoing rollout. These should be resolved quickly and it will be back on for those who had the Retweet feature previously. And we’ll then continue the incremental rollout of this feature to everyone.
Twitter should not be rolling out any new features unless they are able to fix the reliability issues with this application. Millions of users are online using the Twitter and such issues are going to benefit other Competitors like Jaiku from Google. Jaiku provides twitter like functionality in much organized way.