If you’re able to add an exclusion to Norton, you should be able to run System Ninja 3.1 through the installer. We’re currently having some trouble with our advertising parter that is causing false-positive detections in a number of anti-virus products.
The portable issue is still under investigation. The binary files in the installer and the portable version are identical, so it’s not immediately obvious what’s causing this issue. Especially since it’s only affecting a small number of users.