I had Norton and it also did this to me.It drove me round the bend for weeks until I just uninstalled it,its a marketing tool to get you to renew your subscription, and not a very good one really, as many like me just get ****ed off with it and get something else.
I went for the
AVG recommended by some on here,though I have noticed it occasionally seems to take over the computer for its own purposes,updates etc which can be really inconveniant if I'm in the middle of something.