Update: I tried it on my new MacBook. Same result, in Safari (with Verizon instead of Comcast). My Mac has never been on Twitter before, so browser caching is not the issue. Also, Safari was just updated the other day, and the browser is as new as possible.
Second picture: from the DC Metro. Should IT people "pay their dues" with "real jobs", even as volunteers?
Update: May 11
Twitter's back now, for me. I wonder if the East Coast had a major Internet routing problem last night. Both Comcast and Verizon kept stalling, but work OK now (8 AM Wed EDT).