NAV for Mac Auto Protect disabled on Start Up

I used to use Norton Anti-Virus for Mac (v.11) on its own and had no problems. I recently upgraded to Norton Internet Security for Mac (v.4) and now when I startup my computer Auto-Protect and Auto File Scan are disabled. Seems to happen more if I have restarted at some point and then shut down the computer. Tried uninstalling and reinstalling but the problem persists.  I use OSX 10.5.6 on a PPC G4.

 

When I turn off the Norton Firewall the problem seems to disappear. 

 

Any help greatly appreciated.