Why Taurus XL failed

On 24th, February, a Taurus XL carrying NASA's Orbiting Carbon Observatory(OCO) failed to reach orbit. Managers want to confirm there will not be similar issues with Kepler's Delta II.
Preliminary information indicated that the fairing on the Taurus XL did not separate from the rocket as planned about 10 minutes into the flight.
The fairing is a clamshell structure that encapsulates the satellite as it travels.