Hi, reece008.
After turning off Fast Startup, you still have to restart your computer once. Turning this feature off simply means that future startups will be equivalent to cold boots. But currently, if you don't do a restart after having just turned Fast Startup off, you will still be in the, for lack of a better word--pre-Fast-Startup-turn-off stage. In other words, until you do a restart the Fast Startup"turn off" won't take effect, so your problem will persist.
There is also the chance that your Norton may have gotten so corrupted since last month that you may need to reinstall it even after turning off Fast Startup.