Had the same issue. You will notice when you get the error message symantec is trying ot update 2 folders. Both folders load a "full.zip" file and a "full.zip.sig" file in the locations "78648e9d1817017948dc9cc600823543" and "1b42208a6dc8ff67b9a65370351a0457" .
This file then normally would make a "full" folder to extract the file into. From what I saw is the LiveUpdate would fail to make the folder then it reports this error message. To resolve the issue this is what I did.
Created a folder called: "full" in the following locations
C:\Program Files\Symantec\Symantec Protection Center\Inetpub\ClientPackages\1b42208a6dc8ff67b9a65370351a0457
C:\Program Files\Symantec\Symantec Protection Center\Inetpub\ClientPackages\78648e9d1817017948dc9cc600823543
After doing this the zip file would extract to the location and work.
Hope this helps.