Norton/Symantec is notoriously difficult to get rid of!
Even though it may appear uninstalled, it leaves many reminants in the registry and program directory that can cause issues with your new security system.
the presence of uninstalled security software in the Registry can conflict with newly installed security software, and cause system freezes. So can folders of "uninstalled" programs for that matter.
This is what i believe is happening in your situation.
What you need to do is remove any left over Norton/Symantec files and folders from both the registry, the program directory and anywhere else they may lie.