I found the solution for this problem from http://naveenubuntu.blogspot.com/2011/09/waiting-for-jockey-backend-to-exit.html, and you simply need to follow these few steps to manually end the jockey-backend and allows your ubuntu to update software cache.
What is jockey-backend ?
Jockey provides the infrastructure and the user interface for finding and installing third-party drivers which are applicable to the computer. This includes drivers which are added or updated after the release of a distribution, or drivers which cannot be included into the distribution for various reasons (CD space limitation, licensing problems, etc.).
You only need jockey for enabling restricted drivers, afterwards you can safely disable it.
Open Terminal and type following commands:
1) To get into root mode
2) To check the process id of jockey
ps -e | grep jockey
Output: 2982 pts/0 00:00:00 jockey
remember the process id(2982)
3)Type the following to stop/kill the process
sudo kill -9 [process_id]
sudo kill -9 2982