Symantec Antivirus 9.0.0.338 virus definition could not update

Recently, my client windows 98 pc which installed managed symantec antivirus 9.0.0.338, the virus definition stop receive update.

Situation:

-- The Symantec System Center version is 10.1.9.9000

-- The Parent Server version is 10.1.9.9000 

-- The Symantec Antivirus 9.0.0.338 Client mapped by the parent server

Tried method:

1. Tick the "allow this server to manage 9.x and earlier clients....." option on symantec system console(no solve problem)

2. Click the "LIVEUPDATE" button on client pc and run the whole downloading with installing process successfull,but the virus definition still no update(no solve problem)

3. Install an unmanage symantec antivirus 9.0 on win98 pc also cannot update the virus definition.(no solve problem)

Can anybody help me?