Please check your rendering options and see if you have accidentally put a value in any of the "special viewing options"--lateral offset, vertical offset, or offset for roll should all be 0.
You can also try moving your preferences folder to the desktop to see if that fixes the issue. X-Plane will restore the default preferences on the next start up.
Lastly, if none of that helps, please see if a plugin is interfering by moving the plugins folder to the desktop and restarting X-Plane.