It may be just me but I'm not understanding what you mean. How is it you know it's enabled when you "turn off" your computer? Anyhow assuming you know how it's "supposed" to be enabled and it's not working perhaps you might want to try uninstalling it and then reinstalling it. I once had a virus on my machine that when it attacked it dissabled auto protect and then I could not even run virus scans. Anyhow sorry if that was not much help bu all I could think of with what you have said in your post. Also maybe try cleaning spyware and running a full virus scan.