I just had a live chat with a representative from Norton Support.

His explanation was as follow:

the Norton Internet Security 2008 installed on your computer is made up of the advanced technology and all its process runs under the cover in background not allowing the other programs to identify the presence of the anti virus program, this is the protection for the symantec files from being hijacked or modified.

this issue will remain the same even when you run the Symantec online scan, it will not find the anti virus program installed, though it will be working fine.

I tried the Symantec Security Check online. I passed three kinds of check, hacker exposure check, windows vulnerability check and trojan horse check, but failed antivirus product check.

What do you think of it?