Okay, I think I'll be the voice of dissension here. The NYC marathon is not the place to "test out" a hamstring injury.
His cross training/massage/PT has been treating the symptoms, not the cause. He's had this injury for over a year and still does not know what caused it. He has a good idea of what triggers it, but he has not been able to find the root of the problem.
Nate begged his way into Boston this year. He didn't start - because of injury. He then begged his way into NYC. He finished in a time slightly faster than Kara Goucher - because of injury. He apparently has a grudge against the Chicago race director for some reason. He's quickly running out of friends at major US marathons.
I won't go as far as the other poster who said he needs to quit. That's ridiculous. But if he's truly a professional he needs to take care of his injury problem once and for all. His legs are his meal ticket. If he's never able to race at 100%, he'll always go hungry.