If you are finding that Rail Simulator will not start when you press the "play" button during the loading, or that you are getting an error message during the loading process, then this may have been caused by the installation of Upgrade Mk2, which requires you to reset the screen resolution that you wish to use with Rail Simulator. When you attempt to start Rail Simulator you will see a “play...” (which counts down from 10) and “options” button, and if you click on the Options one it’ll bring up a configuration screen – please set the resolution to one that your computer supports, and check this by clicking “test”. If it is an acceptable resolution it’ll then enable the “ok” button and you’ll be returned to the “play.../options” screen and you should be able to click “play” as normal.