True... while I agree with the statement that it is almost never a virus, ironically though, a lot of times it is the anti virus. I myself have had major problems with AVG that causes my computer to freeze dead (mouse pointer, sound, everything) and I've seen many instances of Kaspersky causing programs to stop working.
I don't use Anti-Virus on any of my PCs. I am also not stupid and I don't click on dodgy links or visit dodgy sites or copy stuff from people who have viruses on their drives. Been running like this for years without infection...