Orbital Sciences to Stop Using Suspect Russian Rocket Engine After Explosion(space.com)
space.com
Orbital Sciences to Stop Using Suspect Russian Rocket Engine After Explosion
http://www.space.com/27669-orbital-sciences-rocket-explosion-soviet-engines.html
Edit: just looked at the numbers. The Cygnus is significantly smaller in volume and mass than the Dragon, so I assume now that the answer is "yes, a Falcon 9 could launch a Cygnus"