The following is from WWE.com:
Randy Orton was involved in a motorcycle accident resulting in him re-injuring his collarbone. Orton had initially injured his collarbone last June at One Night Stand, during his confrontation with Triple H in a Last Man Standing Match for the WWE Championship.
As a result of re-injuring the collarbone, Orton will be out of action for three months.
Note: Randy Orton was originally scheduled for a return sometime this month, possibly at SummerSlam, but it now looks like he will be returning at Survivor Series at the latest.