Patricia B,
I'm sorry to read that you're having regular problems with OneCare. You say you are able to restart it. Can you explain exactly what happens? What message does OneCare present? Is this when the computer first boots up or during the day of normal computer use? When you restart it, what are you doing? Opening the program from the Start Menu or somethng else?
You can, of course, contact support to get help looking into the problem, which is certainly not normal.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
I've moved your post to the General folder as it isn't specific to Tune-up, where you posted.
-steve