"Norton antivirus has stopped working" on new installation

I uninstalled an old version of NAV and installed a new version on two HP DM4 laptops running Win7 Home Premium SP1.  On one laptop the program runs as designed.  On the other I get the message, "Norton antivirus has stopped working" when I click "Scan now", "LiveUpdate" or "Advanced".  I have uninstalled and reinstalled several times including once using the Norton Uninstall and Reinstall Tool.  I made no system changes between the old and the new.programs.  Any idea on what I need to do here?  Thanks.