are you using SAV9 or SAV10?
either way, its probably better to copy GRC.DAT to \Documents and Settings\All Users\Application Data\Symantec\Symantec AntiVirus Corporate Edition\7.5 then restart the Symantec AntiVirus service.
If you are using SAV10 then you need to make sure you either have no root certificate on your clients, or the one that matches the server group you are moving them to.
Check that the certificates in
\\SAVServer\VPHOME\pki\roots match those in \Program Files\Symantec AntiVirus\pki\roots - if they don't then either copy the one from the server, or delete the one on the client and restart the SAV service.
hth