Saw the same thing. Warning box came up saying my registration was wrong and that the core game files update had failed. While I went to look for my registration info, I noticed that I was connected and downloading the multimedia files. After everything but the core game files update were downloaded, I selected "Upgrade" for the core files and it worked.
After I rebooted my system, I opened up SDC directly (I'd launched the game and selected the update option the first time) and again received the dialog that my registration credentials were no good. Something screwy with the SDC update?
