Just installed Symantec Anti-virus Corp Ed V9. I had uninstalled V8 before installing V9. Already on my system was Norton Ghost and System Works 2003. Live Update would not work on any of the Norton (Symantec programs). Turns out that the live update used for V9 is different than all previous Live Updates and conflicts with them.
The solution is on the Symantec site (http://service1.symantec.com/SUPPORT/sharedtech.nsf/docid/2000100610540413?Open&src=&docid=2000041710560048&nsf=ent-security.nsf&view=docid&dtype=&prod=&ver=&osv=&osv_lvl=). The old Live update has to be uninstalled and a new one compatible with the enterprise app is also compatible with the other apps. So be aware of this potential problem.