Do you use a registry cleaner? That usually has something to do with it.
Peacekeeper advised in one of the threads to uninstall and reinstall McAfee. There is also a fix available from McAfee but I gather it has to be requested on a per-case basis.
Were you able to get your issue resolved, if not please follow the steps here in this doc http://service.mcafee.com/FAQDocument.aspx?lc=1033&id=TS101209 and you should be alright .