That happend once or twice to me but for me it froze and never came back so I had to do a manual shutdown. If the cc is enabled , try removing all of your cc to a folder on your desktop. Then restart the game as usual, and once your in the hood, save and quit. Move all the files back to your downloads folder and then restart. It will bring up the option to enable the CC, by defualt it will be disabled so you have to select enable and then click OK. The cc will still not be viewable until the next restart. Once your back in the hood go in a lot (any), then once in the lot save and quit. I restarted the computer after the last save and quit. The next time you restart it should show.  Hope that helps.