What operating system and service pack is this and are you totally up to date with both critical and non-critical updates?
According to what I find on Google this was common in the early days of Vista but has happened over the years in other systems and appears to be a system problem rather than a software one.
Try the following:
Step 1 Goto safe mode (may be with networking) by tapping F8 repeatedly while booting up.
Click on Start and in search box type in services.msc and then in menu right click o
services and click on "run as administrator" (ignore that last bit if XP)
Step 2. Double click on "Windows Management Instrumentation" and click on STOP button and stop this service
Step 3 Goto c:\windows\system32\wbem\repository and rename the repository folder
Step 4. Then go to "Windows Management Instrumentation" and click on START button and start this service
Step 5 Restart the computer and issue will be resolved
These are all direct copies of solutions I find using Google.
Alternatively do the following:
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.
Lastly, you could try Technical Support Chat linked at top left of this page or in my signature.