Since installing McAfee Internet Security 2012 (upgrade from 2011, 2010, 2009, etc.), my wife's Dell desktop computer (running XP SP3) during the last several months has experienced a random boot failure about once every week or two, in several cases, the only solution was to restore it from a backup, after which it would be fine for awhile. This is a computer used sparingly with no viruses or malware or shareware ... only mainstream, commercially available software installed (MS Office, Photoshop, iTunes, Norton Utilities) ... This crashing defied resolution until I checked the event log and found a few random "Event 64001" logs; each of these showed-up right before a system crash; on the other hand, at times when there were no logs of "event 64001", there were no crashes. Each and every "Event 64001" recorded that it was associated with McAfee initiating an attempt to write a file to a protected area of the system ... why was it doing this??? Even if it is supposed to do so, it was messing things up badly! Note: McAfee had been fully updated, so no excuse for this.
I removed McAfee Internet Security (with several months active subscription remaining) and replaced it with new purchase of Norton Internet Security 2013 and have not had the problem since, nor have I experienced the phenomenon of the antivirus software taking over the computer with 90+% CPU usage at the most annoying times, something that seemed to start with the McAfee 2009 version and got worse each year.
I cannot recommend this product in its current form. Hopefully McAfee will do a serious overall to fix it before the next version is released.