Issue when runing apt-update with Ubuntu 14.04 LTS

Question

I just installed fresh Ubuntu 14.04 LTS.

When I run apt-get with root user, I get following error shown below.

Any idea how this can be fixed? Please advice.

********Error***********

apt-get update
Get:1 http://security.ubuntu.com trusty-security InRelease
100% [1 InRelease gpgv 66.4 kB] [Waiting for headers]Splitting up /var/lib/apt/lists/partial/security.ubuntu.com_ubunIgn ttp://security.ubuntu.com trusty-security InReleasere failed
E: GPG error: htp://security.ubuntu.com trusty-security InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)