At first I thought this was a joke, but it appears to be for real. From Talk Left here.
The flub apparently made people nervous. Chief Justice Roberts re-administered the oath of office to President Obama tonight, out of an abundance of caution.
Don't worry, the White House says: Obama has still been president since noon on Inauguration Day.
Nevertheless, Obama and Roberts went through the drill again out of what White House counsel Greg Craig called "an abundance of caution."
Shorter version: It was unnecessary but made everybody feel better.