Norton Internet Security no longer working

I have a trial offer on my new HP Pavilion Slimeline computer with Windows 7 Home.  The trial subscription is still good and was just activated on March 22.  The problem is after a download, the Microsoft firewall is now blocking it.  It will not allow me to reactivate it.  I have tried changing permission in the firewall, updating the Microsoft programs and through your website.  Your site cannot find the program to update.  I tried to uninstall the program through the control panel and from the programs menu and neither will do anything.  It won’t run either.  Any ideas how to fix this?