About 25 minutes ago Twitter decided to not work (and still isn't at the time of posting this) - this is more than likely because they're fully applying that update I moaned about earlier throughout the site. Not sure why they need to take this much time as they've surely got test servers to put it on before making it live - luckily for me though, I was able to still use Twitter during these problems because I've obviously made myself a few Twitter-based web apps that process the stuff via Twitter's API (which was thankfully, untouched).
However, I also have a simple idea that's easy to implement and easy for people to then know Twitter's not working instead of them Tweeting "Why's Twitter not letting me do this, or that?".
Look... how simple is that? Just hide the Tweet box and notify us that it's not working - this also saves all that excess load that you're incurring when people are trying to Tweet but can't.
Take note Twitter.