Did you restore old PKI folder in the server..?
If you are not getting clients even after doing all these changes, Replace the GRC.dat & PKI Folder in the cliets.
On the intended parent management server, copy the Grc.dat configuration file from the Symantec AntiVirus program folder.
The default location on a Symantec AntiVirus Corporate Edition server is <OS drive>:\Program Files\SAV.
The default location on a Symantec Client Security server is <OS drive>:\Program Files\SAV\Symantec AntiVirus.
On the client computer, paste the Grc.dat file into the C:\Documents and Settings\All Users\Application Data\Symantec\Symantec AntiVirus Corporate Edition\7.5 folder.
On the intended parent management server, open the pki\roots folder and copy the xxx.x.servergroupca.cer file.
On the client computer, paste the xxx.x.servergroupca.cer file into the pki\roots directory, which appears under the directory that contains the Symantec Client Security files.
After a few minutes, the client finds the Grc.dat file, makes the appropriate changes to the registry, and then deletes the Grc.dat file.
REF:http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2005033015282148?Open&src=tranus_con_sl