New tweets from friends fail to show up in main feed for over 24 hours

In the past 24 hours (its now Monday morning July 21) no new tweets from people I am following show up on the main Twitter page (where normally you see all your friends' tweets. If I manually go to an individual friend's twitter page, then I see their updated tweets...but whatever process Twitter uses to aggregates these into a single feed of all my friends is failed. ANyone else having this problem now. It looks like others have had it in the past -- how do you recover from it?