This is only a guess, but it worked for me down here in the “unassigned media filing center” on the 3rd floor: disable IPv6 in your Network Preferences. Before I did this, I was getting the dreaded “self-assigned” IP; once I turned off IPv6, things magically worked. Don’t know enough to know why.
By the way, the wired Ethernet access down here on the 3rd floor is fast and reliable (unlike the WiFi, which, reports are, is quite flaky and seems to depend a lot on the location of your lap). Easiest way to get down here from up there is to take the elevator that’s just outside the blogger-area exit; get off on the third floor, and walk to your right until you see “Press Filing” on the door.
It looks like it’s possible to get access to the actual “floor” in some sort of rotating fashion. I’m going to try and investigate this next.