That article is incorrect. The launch failure was not due to a fuel leak, but to a failure of the seperation mechanism between the first and second stages of the rocket.
A fuel leak was the cause of the FIRST Falcon 1 failure. This failure was an entirely different problem.
As for why we could recover the payload of the first launch and retry, while we couldnt retry with the second is: alitude.
The first launch failed within seconds of launch, and crashed relatively intact since it didnt reach a significant altitude. This launch worked perfectly until about 1/3 of the way through the flight. Therefore it reached a much higher altitude, and is believed to be unrecoverable.