I am able to update other CC programs but when I try to update Illustrator CC - I get the following error: Download error. Press Retry to try again or contact customer support.(49).
Please refer the thread: http://forums.adobe.com/message/5109299#5109299#5109299 where similar issues has been discussed. If this does not work then you may try applying updates manually from the below mentioned link:
Note: Kindly follow the very important instructions before download.