One day in the early April, I found my McAfee could not do an update.
Error message said McAfee Framework Service wasn't running. Actually it disappeared from Services list.
McAfee was reinstalled successfully with Framework Service, however it still was unable to connect the server to do an update.
After I compared a working copy of McAfee on another PC, I found out SiteMapList.xml didn't exist on my Windows XP - C:\Documents and Settings\All Users\Application Data\McAfee\Common Framework\.
My Vista had the same issue as well. The location is C:\ProgramData\McAfee\Common Framework
After SiteMapList.xml was copied over, it has been working well since then.