Follow the steps below to resolve the issue:
 

1. Uninstall and reinstall the LiveUpdate that was shipped with the version of SEPM installed.
2. Register SEPM with LiveUpdate after re-installation of LiveUpdate via the
   Control Panel > Add or Remove Programs > Symantec Endpoint Protection Manager > Change > Next > Repair.
3. Register the SEP Client with LiveUpdate after re-installation of LiveUpdate
   Control Panel > Add or Remove Programs > Symantec Endpoint Protection > Change > Next > Repair.
4. Please confirm if there is a Proxy Server - This will affect the setting used by the SEPM Server.
5. If there is a a Proxy Server then, following one of the below items:
   • Bypass Proxy
   • Configure the Proxy to have the LiveUpdate

• Uninstall and reinstall LiveUpdate:

Warning: Uninstall-Reinstall of LiveUpdate may affect the LiveUpdate functionality of other Symantec Products installed on the same system

1. In Windows Explorer make a back-up copy of the following file:
   C:\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate\Product.Inventory.LiveUpdate
   
   Note: that on some newer Windows Operating Systems, this file is in
   C:\Program Data\Application Data\Symantec\LiveUpdate\Product.Inventory.LiveUpdate
    
2. Click Start > Settings > Control Panel.
3. Click Add or Remove Programs.
4. Click LiveUpdate.
5. Click Change/Remove.
6. Follow the on-screen instructions to uninstall LiveUpdate.
7. In Windows Explorer, delete the following folders if they are present:
   C:\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate
   C:\Program Files\Symantec\LiveUpdate
   C:\Program Data\Application Data\Symantec\LiveUpdate
   
8. Install LiveUpdate using LUSETUP.EXE located in the SEP installation files, in the following folder:
   ...\SEPM\LUSETUP.EXE
9. Browse to:
   C:\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate\Product.Inventory.LiveUpdate (or C:\Program Data\Application Data\Symantec\LiveUpdate\Product.Inventory.LiveUpdate)
   
   and replace the newly created Product.Inventory.LiveUpdate file with the file backed-up in step 1.
    

Note: If you did not back-up the Product.Inventory.LiveUpdate file before deleting the LiveUpdate folder,  then the SEPM and/or SEP must be re-registered with LiveUpdate for it to update correctly.

• Register SEPM with LiveUpdate after re-installation of LiveUpdate:

1. Click Start, then Run.
2. Type cmd, then click OK. This will bring up a command prompt.
3. At the command prompt type cd and the path to lucatalog.exe. By default the command would be:
   
   cd C:\Program Files\Symantec\Symantec Endpoint Protection Manager\bin
   
4. Type lucatalog.exe -update

• Register the SEP Client with LiveUpdate after re-installation of LiveUpdate:

1. Click Start > Settings > Control Panel.
2. Click Add or Remove Programs.
3. Click Symantec Endpoint Protection.
4. Click Change.
5. Click Next, select Repair, and click Next again.
6. Click Install.
7. Click Finish

• At times it is found this issue to occur due to a Proxy blocking the LiveUpdate connection, Please confirm if there is a Proxy Server:

If there is a Proxy Server then, then there are 2 choices:
 

1. Bypass Proxy
2. Configure the Proxy to have the LiveUpdate

• To Configure the Proxy server from Symantec Endpoint Protection Manager.

1. Click on Admin
2. Click on Servers
3. In the "view servers pane" select the name of the Manager under local site
4. After selecting your server, in the tasks pane, click on Edit Server Properties, a dialog box will open up
5. Click on Proxy Server
6. Fill out the appropriate settings and credentials for HTTP and FTP as required for access.

• To Configure the Proxy server from LiveUpdate Application.

1. Click on Start
2. Click on Settings and Go to Control Panel
3. Click on Symantec LiveUpdate
4. Go to the HTTP Tab
5. Select the right configuration as required.

Note: Try Domain qualified user name like “domain\administrator” rather than just “administrator”. After configuring it this way, LiveUpdate should be able to pass through the proxy.

References
Title: 'How to Uninstall and Reinstall LiveUpdate When a Symantec Endpoint Protection Manager or Symantec Endpoint Protection Client is Installed'

Document ID: 2007100907303548
> Web URL: http://service1.symantec.com/support/ent-security.nsf/docid/2007100907303548?Open&seg=ent

Title: 'How to setup the Symantec Endpoint Protection Manager to use specific proxy settings for LiveUpdate'
Document ID: 2007082113383448
> Web URL: http://service1.symantec.com/support/ent-security.nsf/docid/2007082113383448?Open&seg=ent