This is one of NASA's gas stations boys filling Discovery's external tank with 1.6 million pounds of liquid fuel. The procedure had to be stopped yesterday, further delaying its launch. I wonder if he cleans the windshields too.
The source of the problem may be the hydrogen fuel valve. In particular, NASA says it may not be the valve itself—which according to telemetry refused to close—but with the instrument that monitors the valve. According to NASA's Mike Moses:
When we went to close the valve (after the hydrogen tank was full) we didn't get an indication that it was closed.