It's a Windows problem as far as I can recall and a very old one too.
Is this Windows XP SP2 (or 3) by any chance?
There's a KB article at Microsoft regarding it here: http://support.microsoft.com/kb/899865
It can also happen in Vista, see: http://answers.yahoo.com/question/index?qid=20100119091043AAZjRsV
It helps us to help you when posting to give full details of your operating system and service pack, plus version numbers of the installed McAfee software.
Meanwhile, if you're in the habit of running registry cleaners, stop now. They do more harm than good, believe me, and often cause issues such as this.