In fact, the API seems to be really borked at the moment. I've been running more tests on friends_timeline.json, and the following happens:
1) Sometimes the connection is refused. 2) Sometimes I get a 200 OK with an empty JSON array, and seconds later with the very next call on the same Twitter account I get a 200 OK with a fully populated JSON array. 3) On some accounts I get "401 Invalid / expired token", where the token on my side has not changed and the connection is present in the Twitter account's Connections tab.