We've been getting reports from developers that the API has been suffering from elevated latency, and in some cases have heard of requests failing completely.
This is clearly a high priority issue, and is being actively investigated by the team at Twitter HQ. We'll post updates on Twitter http://twitter.com/twitterapi and to this mailing list when we have them. Thank you to all the developers who have provided us with examples and datasets of where this has happened to them. Matt Harris Developer Advocate, Twitter http://twitter.com/themattharris