My guess, understanding I'm not a computer expert -

You may have spyware, not all versions of Norton may address that. I used to use Spybot, which picked up all kinds of weird stuff when it scanned (daily), but I changed to Windows Defender. Neither interfere with Norton operating.

If you don't have a spyware program

Ad-Aware

Spybot Search and Destroy Scans, removes, and prevents spyware.

Windows Defender Scans, removes, and prevents spyware. This is a good program for me, but you can only get it if you have Windows 2000 or XP

SpywareBlaster

CWShredder

All are freeware

1 Make sure you have the latest virus definition files for Norton.
2. Once you have updated virus definition files, run a full scan again.
3. Look in the audit log on Norton and find the name of the beast that is infecting your computer.
4. Check the Norton website to see if there is a removal tool for said beast.
5. If a removal tool or other "fix" exists, execute same.

A pain isn't it? I don't know how much money my company makes out of fixing infected computers per week, but its a substantial sum.

Thank goodness it's just your computer. I thought maybe another post fell on you! I am glad you're ok.
K