I highly recommend purchasing a new version of X-Plane. Laminar Research has poured incredibly large time and and effort into the new versions, and continues to support X-Plane 10 (with X-Plane 11 coming out within the next one to two months).
I would also understand if you prefer to stick with X-Plane 8. This error seems to be originating from the root library folder. The easiest way I can recommend is to run the installer/updater application. This can be found here: http://www.x-plane.com/desktop/try-it/older/
1.) Scroll to "Download X-Plane 8 Updater/Demo Installer"
2.) Select "Download For Windows"
3.) Run the installer; this should locate corrupted, modified, or missing root-folder files, and replace them with the correct version. This should fix your issue.
If not, please notify me.