Personally, I have never had issues with Norton, but that doesn't mean it can not happen.
The reason I suggested Checking for a New version, or updating is because your Desktop Icon and and taskbar Norton Icons look different from mine. As if a older version, or it was 360.
One reason I was thinking there may be a issue here.
If you purchased a key from Norton, you should be able to download the latest verion directly from the website.
Perhaps there was something wrong with the version Comcast uses? Not sure.
At any count, MSE is a good AV as well, so its just a matter of which you prefer.