I doubt that a new hardware installation would cause your Norton protection to malfunction. It might be because of the drivers/software that came with the sound card that interfered with the Norton Auto Protect feature. Try uninstalling all of the software but leave the actual hardware in your computer. If you still have the problem, try removing the hardware and seeing if the Auto Protect Feature works. Maybe it could be the hardware, I'm not sure. I hope this helped.
Yup, had the same problem, my Norton would not enable me to load certain programmes, and this was after a clean install. Got onto Norton, an they said the only fix was to un-install, then re-install - tried it and it worked a treat.