Norton 360 won't respond and gives error 8504, 104

Today, once again, I was unable to open my Norton 360 program. I could not get it to respond in any way and eventually a window showed up with error code 8504, 104. This directs me to instructions to use the Norton removal tool and then to re-install my program.

My problem and concern is that this has happened before and I have already gone through this. I need to know what caused this. I just discovered this but it could have been like this for days or weeks. Does this mean that I have had no virus protection? If something is shutting down my anti-virus program this easily and with no warning then what am I paying for?

Thanks for any guidance...............