Try two of the Three R's. Reboot, and if that doesn't work, Reinstall. Personally, when it comes to Malware removal and/or detection, I prefer to use Malwarebytes, or Microsoft Security Essentials. I'm not going to lie to you, most anti-virus software is total crap. In the past, software I've paid for did a far worse job detecting and removing malware than free software I found online. I definitely recommend getting better antivirus software than Norton whether or not rebooting and/or reinstalling fixes your problem.