Yesterday, users reported that Google Reader was not refreshing feeds and TechCrunch picked up the story. A Google Groups thread has also been monitoring the downtime, eventually with Mihai Parparita, a Google Reader Engineer, informing the community that the problem has been resolved.
Very sorry about this, feeds should be correctly refreshing again. They will catch up on updates over the next few hours.
Google Reader also suffered from an outage on June 12th.
Forum discussion continues at Google Groups.