From Pro Football Talk and noted here by scout Bob Harris:
A league source tells us that Cowboys receiver Roy Williams suffered a broken collarbone during his Thursday night collision with cornerback Orlando Scandrick.
Typically, a broken collarbone requires a healing period of six to eight weeks.
UPDATE: Another source tells us that the X-rays were negative. Our original source insists that it's a break, and that Williams will miss 6-8 weeks.
SECOND UPDATE: Williams told multiple players it was broken. X-rays reveal otherwise. MRI coming tomorrow. Sorry for the confusion. It's one of the hazards of real-time reporting, and it's one we'd like to avoid.