Came across this silly little thing about a week ago and had to dig for an hour or so to fix it. After I updated my nvidia drivers, my taskbar suddenly went from my left screen to my right screen. (I have a multi-screen setup).
In order to fix this, try holding down the ALT key when you click and drag the task bar… keep it held down through the drag. It will allow you to move the taskbar back to the position that you are used to.