Houzhi Shan,
Since you marked this thread as Answered, I understand that you do not need to proceed further at this time.
You can download updates to a Flash Drive and carry them to your computer. There have been many improvements since CCSv5.1 and the emupack's have been updated, also. If you continue to have problems, please update these as the first thing to solve any new problems, or if this problem continues.
Regards,
RandyP