Norton AntiVirus (NAV) has the ability to detect unknown viruses of various types using heuristic algorithms known as Bloodhound. This technology was developed by Symantec Security Response.

http://securityresponse.symantec.com/avcenter/venc/data/bloodhound.html

You state that Norton is rejected access to repair it, which would lead me to believe that it is possibly inside a System Restore file. In that case, disabling System Restore will remove it.