This site is being deprecated.
Please see the official X‑Plane Support page for help.
Please make sure you only update X-Plane through Steam and not with the installer available at X-Plane.com.
10.50 has had some issues with preferences getting messed up. You can try finding your X-Plane root folder (instructions here), going to the Output folder, then the preferences folder. Delete X-Plane Screen Res.prf and see if that helps.
This site is no longer being actively maintained.