Google, is there anything it can't do. :)
It's really weird. This happens every once in a while to some folks ... there's got to be a setting somewhere that triggers this. Something I set somewhere that I'm not associating with this.
It's not a big deal at all really. The audio engine is running anyway whether it's playing or not. I thought there was a way to turn that off when you weren't playing a project, but I can't find that setting, so I must have been dreaming it.