Tried a full page reload earlier with no success. But if it's working for you guys, I'll try when I get home tonight and see if it's working from there. If it does work at home, I suspect I know what the issue probably is. Twitter is blocked by the firewall here at work if you try to access it using "http://". It is not blocked if you try to access it using "https://". (YouTube, Facebook, and a few other sites behave identically.)
Call it a hunch.