It could be just about anything causing something like that, but I can assure you that it isn't normal behaviour.
It could be infection, check for spyware using the free version of this tool:
http://www.superantispyware.com/superantispywarefreevspro.htmlIt could be shortage of available memory or hard drive space. The minimum is stated as 128mb of RAM but we recommend 256mb or more as the bare minimum. HDD space should be at least 75mb free.
It could be competing software, see this list:
http://service.mcafee.com/FAQDocument.aspx?id=307274&lc=1033&partner=10005&type=TSIt could be the practice of operating two of anything, firewalls, pop-up blockers etc.
The installation could be corrupted in which case 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
4. Reboot and redownload/reinstall your McAfee products directly from your account at the McAfee web site, not from any CD that you may have.
Or a combination of any of the above.
Your best bet is to contact Technical Support who can escalate the case and even go into your machine if necessary.
Link at top left of the page or in my signature.