Some Internet proxy servers require you to enter a username and password to authenticate. McAfee products are not able to simulate this process, causing updates to fail and signature files to be out of date.After 8 days, the McAfee protection status icon will be displayed in the system tray. Double-clicking the icon will open McAfee SecurityCenter which will report the problem: Your signature files are 8-29 days old.
Please follow the below steps to update the virus scan:
1.Check whether the system clock is set right
2.Check and delete if you find any other secuyrity software in C:/program files & comon files.
3.Run the tool from http://download.mcafee.com/products/licensed/cust_support_patches/MSCPRXFIX.exe and restart the computer.
4.open security center & check for updates.
Kindly report back if you have any issues.