Georges St. Pierre learned a few hours ago that Matt Hughes is injured. So the rumor of Hughes injury, which went out after the UFC 63 : Hughes vs Penn, would be a confirmed fact.
We don't know which type of injury it is, neither if this could compromise his title defence against St. Pierre on November 18th. But if the contender was officially informed about Hughes injury, this could mean that the fight will probably be cancelled.
source: http://www.ultimefanatic.com/modules/news/