NAV 11.0 & OS 10.6.8 Error Messages

I got a Mac Mini from Apple, and tried to install NAV 11.0 for Mac from a purchased CD, since the OS is 10.6.8.  The installer asked to install Rosetta, I said yes, and then completed the installation, ending with restart.  Upon return to desktop, this error message starting popping up, and returned again every time I dismissed it:  "Norton Antivirus Error:  Norton Antivirus Auto-Protect could not continue.  Please run LiveUpdate or reinstall Norton Antivirus and restart.  (Code: 10)".  When I tried to run LiveUpdate, Update everything (in between dismissing the repeated pop-ups of the error message), I got this error message:  "Updating error.  There was an error performing the update."  When I tried to open NAV itself, I got this error message:  "Norton Antivirus could not open its preferences.  Please try restarting your computer.  If this error persists, please try re-installing Norton Antivirus."  I have tried multiple restarts, and two reinstalls, with no improvement.  I found one suggestion to do a "Get Info" on the NAV application, and uncheck "Start in Rosetta".  Box was already unchecked, so I checked it, tried a restart, no improvement, then unchecked it, tried a restart, no improvement.  Symantec clearly says the NAV version for 10.6 is 11.  Help?!?!