There is a thread here about Norton AV not being able to delete or quarantine a virus.
Last night i saw a PC running McAfee (all up to date and set up correctly) which had a virus running on it. However McAfee had no alerted the user of it presence. It had got on to the PC and then started with every boot up for a while - not a peep from the AV.
It was only when i saw the suspicious entry in the Startup list and i specifically asked it to scan the file that it announced "Virus Found!!"
McAfee then also told me it couldn't delete or quarantine the virus. I had to remove the startup entry, reboot and then get the AV to work.
If i was less PC savvy then i would be stuck!!!
AVG Free Edition has never let me down so why do the "big AVs" of Norton and McAfee behave like this?? Surely Norton or McAfee should be able to shut down a running virus and kill it??