There a 5 fixes in the 'Blank' link in my signature below and the first one usually fixes the problem instantly.
A sixth chance would be to try running the Virtual Technician if all those fail : http://mvt.mcafee.com/
Thanks for reply,
While checking system, I observed that previous antivrus version of MCaFee was not properly uninstalled. I uninstalled Total Protection 2013 , Cleared recycle bin and again installed MCaFee Total Protection 2013 & now it is working fine.
That's good. Good luck.