I've seen that happen here sometimes after an update.
Make sure your system clock is accurate and that Windows is totally up to date, including any updates for Internet Explorer. Even if you never use IE, McAfee does in the background.
Try a complete shut down and restart then run the Virtual Technician to make sure all, is OK.
http://mvt.mcafee.com/ (assuming this is the home product as it doesn't use DAT's, I assume you meant that you manually updated it by clicking that option in the UI).