As far I as know, the answer is know. You have to copy the grc.dat file from the parent server's vphome share to the workstations documents and settings\all users\application data\symantec\norton antivirus corporate edition\7.5 directory. I normally stop the antivirus service on the workstation, copy the grc.dat file then start the service. The workstations antivirus service will read the grc.dat file an point the client to the new parent server and delete the grc.dat from the 7.5 directory.
HTH - Stiddy