The Ubisoft forums have an apology from Ubisoft for an outage in the Uplay service, which failed to live up to its name as Ubi's online DRM servers went down over the weekend, preventing their games from being authenticated and leaving them unplayable. Word is: "The Uplay PC service should now be up and running properly. Please try logging into your game and let us know if you have any issues," and word on Destructoid is that this us due to demand from the ongoing Steam sale, supported by Steam Support's retweet of Ubi's tweet about the outage (thanks Chris via Reddit).