It must have become corrupted. This can happen if you have at any stage used System Restore, or a Registry Cleaner (I do not recommend those at all) or there is competing software present.
Also check that you System Clock is accurate both time and timezone-wise.
As Security Center relies on Internet Explorer to work properly go to IE8 (which I assume is the final version?) Tools/Advanced Options and click the Reset button and OK any prompts, click Apply and OK. Close and reopen IE. Go to Tools/Manage Add-ons and re-enable the add-ons.
See if that helps.
If not, then do the following after enabling temporarily Windows Firewall:
1. Uninstall all McAfee programs through "Add or Remove Programs" in Windows "Control Panel".
2. Use the MCPR tool, see this article: How to remove supported McAfee consumer products using the McAfee Consumer Products Removal tool (MC...
This will remove all McAfee remnants from your computer. (you must have Windows Vista, XP or 2000 SP4 to use this tool)
3. Launch Windows Explorer and delete all McAfee files in "Program Files" but especially in "C:\Document and Settings\<user>\Application Data" and "C:\Document and Settings\All Users\Application Data". You have to set Windows Explorer to show all hidden files and folders (Tools > Folder Options > View tab). Just delete the McAfee folders even if they are empty in all the "Application Data" folders. Can be more than one!
In Vista: C:\Program Files, C:\ProgramData and C:\Users\yourname\AppData\Roaming
If you can't find these files don't worry. It just means that MCPR has done its job.
4. Reboot and redownload/reinstall your McAfee products directly from your account at the McAfee web site.