Firefox is locked.I get a message"Settings being managed be Vendor Norton"

Hello Everyone

Firefox does not seems to be working and I can't get access to settings as I get the message that "Settings are being managed by Vendor Application Norton". I am also unable to download any programme as I get the message "Internet security does not allow programe downloading". I had problems with  NIS two days ago but managed to get it working now.

I have an HP window 7 bit 32.

Thanks