More as we learn it.
Update: We were heading into the hall, and saw an alarm go off. The guards at the doors started turning people away, and when we asked what was up, we were told it was a fire alarm and that we should exit the building. There's still no action in the press room (and they haven't interrupted the class panel on the floor), so it's likely a false alarm.
Update2: Whoops, the class panel is being held upstairs, not on the convention floor. We just sent our man Adam Holisky down to see what the ruckus is all about and get the inside story. It's good having bloggers to boss around, and nice to know they'll even walk into possible injury to do what we say.
Update3: A security guard told Holisky that somebody tripped something they weren't supposed to, and they are now letting people back onto the floor. Crisis.. averted!