According to a NASA press release, the space program governing body lost communication with the International Space Station this morning around 9:45 AM EST. While the situation sounds frightening, NASA made sure to note that the communication breakdown happened during a routine onboard software update, and that the flight crew was able to make contact with Mission Control Houston when the station flew over Russian ground stations before 11:00 AM EST:

The primary computer that controls critical station functions defaulted to a backup computer, but was not allowing the station to communicate with NASA's Tracking and Data Relay Satellites. Mission Control Houston was able to communicate with the crew as the space station flew over Russian ground stations before 11:00 a.m. EST and instructed the crew to connect a backup computer to begin the process of restoring communications. Expedition 34 Commander Kevin Ford reported that the station's status was fine and that the crew was doing well.

Canadian astronaut Chris Hadfield tweeted this from about the ISS around 1:45 AM EST:

Presumably they were prepared for this sort of temporary lapse, and everyone's going to be fine.

Update: Communication systems have been restored as of 12:34 PM EST.

[Source image from NASA.]