Err: apt-get update not working

Error:
    Failed to fetch http://security.ubuntu.com/ubuntu/... Could not connect to localhost:4001 (127.0.0.1). - connect (111 Connection refused)

Reason:

    Anon-proxy server may be run

Solution:

    Uninstall or stop the service and try.


    Ref: http://ubuntuforums.org/showthread.php?t=898375