This problem keeps persisting 5months ago

Every time my computer goes idle it does a deep scan by itself. Yes I have Norton 360. Now the next morning I wake up and find out that my fonts have been changed to italics. Why? Because Norton deletes the Arial Font and leaving the Italics up front for default. This problem has been persisting and I dont know how to change it. I always have to do a system restore when it happens. Please someone help me..........